


A Peculiar Crossroads

by TheRechercheRambler



Series: A Chance Meeting [4]
Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Gen, this one's got a lighter tone than the last two I think, will be updating every four days for the foreseeable future, your regularly scheduled crossover shenanigans have returned
Language: English
Status: Completed
Published: 2016-03-01
Updated: 2016-04-10
Packaged: 2018-05-24 03:57:50
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 11
Words: 19,774
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6140770
Author URL: https://archiveofourown.org/users/TheRechercheRambler/pseuds/TheRechercheRambler
Summary: <blockquote class="userstuff">
              <p>After a full year without any interdimensional incidents, the hapless worlds of Undertale and Underfell suddenly find themselves colliding yet again, leaving many monsters scrambling to find a way to get back to their proper places.</p><p>So that everyone's up to speed on how things work and how the Underfell characters have developed, I highly recommend reading the first two fics, A Novel Experience and A Path to Redemption, before reading this one.</p>
            </blockquote>





	1. Chapter 1

It was a very nice day on the Surface, at least as far as the inhabitants of the town atop and about Mount Ebott were concerned. The sky was a deep and clear blue, the weather was mild, the breeze was light, so generally speaking it was almost painfully picturesque.

The Barrier had been broken over a year ago, and by now monsterkind was once again thriving and flourishing alongside its less magical counterpart. Their once-small settlement had expanded in the space of that year, growing to surround the entire mountain, and was now home to both humans and monsters of every variety.

Frisk and Toriel were at home, and had been trying to enjoy the quiet morning as much as they possibly could, what with having the vilest houseplant known to man for company; Mettaton, who had just arrived back in town to visit his cousin, was having some wear and tear fixed up over at Alphys and Undyne's house; Undyne herself was out for a jog; Asgore was tending to his garden; and Sans and Papyrus were late.

To be more specific, they were stuck in a long, slow-moving check-out line at a local grocery store. To be more pertinent, they were in the process of buying ingredients that they'd need for the cooking they had been planning to do with Toriel roughly ten minutes from then. As it stood, they were at a standstill, and even when- if- they got out of that blasted line, it was going to take them a lot more than ten minutes to get to Toriel's house even if they ran the whole way.

Eventually they managed to make their purchases and their escape from the grocery store, with only about a minute to go until the time they'd hoped to arrive at Toriel's house.

“SANS!!! WHAT ARE WE GONNA DO?! WE'RE GONNA BE SO LATE!” Papyrus asked, his anxiety over being late growing with each ticking second.

“i s'pose it's _time_ to take a shortcut, bro.” Sans said.

While he wasn't anywhere near as worried about being late as his brother, Sans was actually somewhat close to looking forward as much to the cooking hangout. With any luck, it would help him take his mind off things, such as the fact that no timelines had ever progressed this far in the past, and that therefore they were probably long overdue for a reset. An opportunity to pretend otherwise, and make the most of this peculiar timeline while it lasted, was a very welcome one.

Papyrus's sockets narrowed slightly, and the corners of his mouth seemed to turn down (whether or not they actually could, what with him being a skeleton and all, is a question best left for another day). He'd only had to follow Sans on one of his “shortcuts” once in that run, and he hadn't enjoyed it all that much; but if it meant being punctual, then some brief weirdness would be worthwhile.

“FINE.” he said.

Sans meant for the shortcut to take them straight to Toriel's doorstep, but as he made the short trip through lower space, he felt a shockwave rush through him, like someone had just detonated a bomb within the fabric of space and time. Immediately after that another, less forceful shockwave hit him.

As quickly as he could Sans pulled himself and Papyrus back to normal space. The whole thing had taken place in under two seconds.

“SANS!!! WHAT HAPPENED?!” Papyrus asked. “THAT WAS EVEN WORSE THAN THE LAST TIME!”

They were standing near the corner of a street that was bent at a right angle, with houses lining either side, just in the same way as their own street. There was even a large house on the corner with a wrap-around porch, just like Toriel's house. This house was roughly the same size as Toriel's house, although it was built in a slightly different style, and painted mostly in dark shades of purple with a bit of black here and there. Many of the other houses on the street that Sans could see were similarly moody, although here and there were a few bright homes which stuck out thanks to their sheer deliberate cheerfulness. He felt a sinking feeling where his stomach would have been, if he had one.

“THIS…” Papyrus wore an expression of utter bewilderment as he looked around. He, too, had noticed the odd aesthetic of their surroundings. “WHERE IS THIS??? THIS ISN'T BE OUR STREET.”

“heh… no, i s'pose it isn't.” Sans said.

As he looked around, he realized that around the corner he could hear people talking. These escalated quickly, gaining in volume and in anger. Soon they had gone from conversing to shouting, and were joined by the sounds of battle. Papyrus's sockets widened when he noticed them.

“hey, papyrus.” Sans said quietly. “remember a year ago, when we met those skeletons who looked kinda like us, but angrier? and edgier?”

“AND MORE VILLAINOUS. AND SADDER, I THINK.” Papyrus added, keeping his voice down somewhat so the brawlers around the corner wouldn't notice them. “OF COURSE I REMEMBER THEM! WAIT-”

He looked up and down the street once more, as if seeing it with new eyes. Then, he let out an exasperated sigh. “WE'RE IN THE EVIL TWIN WORLD, AREN'T WE?”

Sans nodded. “shortcut went wrong, somehow.” he said. “sorry.”

“WHAT DO WE DO NOW???” Papyrus asked, glancing nervously in the direction the sounds of the fight were emanating from. “HOW'D YOU GET BACK LAST TIME?”

There, they were both equally stumped. Over the past year, Sans had tried several times to call one of the strange entities- which version, theirs or the other world's, didn't matter too much- to no avail. Frigid fear crept over him; it had been bad enough, a year ago, when he'd been trapped in the other world alone without a clue of how or if he'd get back home, but now that Papyrus was stuck there, too…

Well, there was no need for Papyrus to worry about that. As usual, Sans masked his fears with his permanent grin. He glanced down at the bag of groceries he was holding; there were some snails among them, which Toriel had requested they pick up before they started.

“welp. we'll figure something out. Shouldn't be that hard to escar- _got_ home.”

Papyrus glared at him.

“THAT WAS LOW, EVEN FOR YOU.”

 

Back in their world, Undyne's jog had taken a turn for the weird. She was only halfway back to hers and Alphys's house when suddenly the world blurred and faded into nothingness around her. The fish monster felt a yanking sensation in her gut, as if she was being pulled somewhere from the inside-out. It was over in scarcely a second, but the street that she was standing in when the world decided to go back to its proper place was not the one she had been jogging down moments ago.

She stopped her run immediately, of course, although her momentum carried her a few steps farther. Undyne's eye widened as she looked around; this street had the exact same layout as the one she had been on, but all of the buildings looked almost completely different.

“Wha…?” she said. Then, she swore colorfully and loudly.

A curious scratching noise from somewhere behind her caused her to jump involuntarily, and she whirled around, summoning a spear to her hand.

“HEY! watch where you're swinging that thing!”

Undyne narrowed her eye, still tightly grabbing her spear in both hands, and her face twisted into an angry frown. “Sans?! What the HELL is going on here?!”

**Notes for the Chapter:**

> Shoutout to my friend Good-Golly-Gee for suggesting that baking be the reason that Sans and Papyrus were late! I was really stuck on that one for a while.
> 
> There's going to be way more people crossing over this time around, and hopefully many meetings with counterparts. I don't think I can have everyone meet their alternate self, but many of them will.
> 
> Because there's a lot of crossovers and interdimensional hijinks going on here, I'm going to list which character is known to be in which universe at the end of each chapter. Thanks to Iridium_Phoenix for the suggestion. At the end of this chapter, Sans, Papyrus, and Undyne from Undertale have been transferred to Underfell.
> 
> Chapter 2 will be up on Saturday.


	2. Chapter 2

**Summary for the Chapter:**

> Undyne and Underfell Sans get along about as well as oil and water; meanwhile, a certain human and flower discover they're not where they should be.

In the world that Sans and Papyrus were now trapped in, the day had begun fairly well. This monster settlement about Ebott was smaller than its thriving counterpart, and home to far fewer humans. The monsters of this world had been overjoyed to have their freedom at last, and to be able to enjoy it peaceably at that. But a civilization's worth of people can't change their ways overnight, and in spite of their eagerness to turn over a new leaf when they got the opportunity, most of them still realized that if they simply rushed into meeting with the humans, things would quickly become unpleasant.

So while they struggled to cooperate and build another new home for themselves, their new Queen and young Ambassador met with the humans alone. Toriel had the political and diplomatic experience the human did not, and Frisk of course had the ability to persuade and befriend which in Toriel had done nothing but gather dust for years. Negotiations proceeded slowly, but surely, and monsterkind remade itself in preparation for the days when it could meet humankind in friendship again.

Of course, just because they were trying to learn how to be kind and understand more about these things called “morals” again didn't mean that everyone was suddenly sunshine and daisies. They were not quite so bad as a playground full of middle schoolers, and far less violent than they used to be, but they were still rough around the edges and highly prone to feuding.

Frisk's sort-of family was no exception. They may have done everything in their power to keep their monster friends wrapped around their little finger, but that didn't do much to keep them from bickering amongst each other.

It was due to one of these quarrels that that morning saw this world's Sans storming out of Toriel's house, muttering irritably as he went.

He didn't go far from the doorstep before he teleported away, not really caring where he ended up so long as it was well away from the boss monster and their argument. But, of course, his plans of sulking angrily were thrown awry when he felt space practically explode about him as he took his shortcut.

The town he found himself in had a much calmer, more friendly-seeming aesthetic than his own. Back home, houses which were still stuck in the old edgy Underground rut clashed next to others with aggressively cheerful colors. These were owned by monsters who wanted all the world to see that they were making a change, but didn't yet have a firm grasp on how to do it without making others' eyes bleed.

“you've GOT to be kidding me!” he growled when he saw this, as a pool of fear bubbled up within him.

He immediately tried to cross back to his own world, just in case; the fabric of space time burst outwards around him once more, and to his immense relief the street that hit his eyes when he returned to normal space was painful to look at.

Then he realized he was not alone; Undyne was also there, wearing sweat pants and a white tank top, and her ponytail was slightly less wild than usual. She heard him arrive, and instantly turned on him, ready to skewer him on one of her spears.

“HEY! watch where you're swinging that thing!” he said, taking a step back and watching her warily. These days, ever since Frisk had befriended her, Undyne usually went on the defensive when confronted, not the offensive.

Undyne stopped glaring at him, but her confused expression was no less intense than her angry one. “Hey, Sans?! Do you know what the HELL is going on today?!” she demanded.

“w-what d'you mean?” he asked, shrinking back. He had a terrible sinking feeling.

She raised her one visible eyebrow incredulously. “Wha-? Look around! The whole street's messed up! Something weird just attacked me out of nowhere, and” She let go of her spear with one hand gestured vaguely at him. “what the heck are you wearing?”

Sans's sockets went dark. This was going to be a long day.

 

Only a few moments after Sans stomped out of Toriel's house, Frisk left to follow him, Flowey around their shoulder as usual. They didn't really expect to get out in time to talk to him before he inevitably vanished, but it was worth a shot. But they scarcely had time to close the front door behind them before their friend disappeared before their eyes, and they were simultaneously shunted sideways through space and time. Back in their own world, a different Sans and Papyrus had suddenly shown up where they had been standing, and Frisk was left blinking in surprise at their slightly new surroundings.

“What was that?!” Flowey asked.

Frisk took a deep breath to keep their nerves calm. Whatever weirdness was going on, it surely couldn't be worse than when they'd been Underground. They turned around, and after only a moment's hesitation, knocked on the door of the house that somewhat resembled their own.

Their knock was answered by a tall goat-like monster wearing a light purple dress. Frisk's eyes widened; this monster might have been their mom's twin.

The boss monster blinked rapidly and drew back their head when they saw the unusual pair on her porch. She looked back at something inside her house, before looking back at Frisk and Flowey.

“H-hello, little one.” she said kindly, in spite of her clear confusion. “Are you a friend of Frisk's…?”

“Huh…? My name is Frisk,” Frisk said. “Ms… um…”

“Toriel.” the monster replied. As she did, another human child came up to the doorway from behind her. They were of Frisk's height and complexion, and even had the same haircut. The only difference was that this child's sweater was light blue with purple stripes, while Frisk's sweater was black with red stripes. They might have been identical twins.

The two humans stared at each other for a moment, Frisk in shock, the other slightly surprised but otherwise remarkably chill about meeting their doppelganger, while the Toriel looked at them both with bewilderment.

“Where did you come from, child?” Toriel asked Frisk.

“Oh dear,” Flowey mumbled, and Frisk quite agreed with his assessment.

“Um.” Frisk started. They quickly whipped up some tears, to delay having to properly answer the question, and to get the strangers' sympathy. This Toriel seemed friendly enough, but their experience in the Underground had shown them that you could never be too careful when trying to keep people from killing you. “I… I d-don't know… w-where is this?”

“You poor thing!” Toriel said, offering Frisk her hand. They took it, and let her lead them inside.

The room they entered was somewhat large and carpeted. To their left Frisk could see a family or living room with a large sofa, and to their right was the kitchen. In the first room was a bench by the window and a large round table in the center with a number of chairs around. A book laid at one seat; in their haste to leave it, the person who had been reading it had evidently stuffed their phone inside it to mark their page.

There was also a flowerpot, with a very angry golden flower sticking out of it. He glared at Frisk and Flowey in irritated shock.

“Who the heck are you?!” he demanded.

Flowey's grip on Frisk's shoulder tightened. He gulped, and said, “H-howdy! I'm-”

“Flowey. Flowey the flower.” the other golden flower finished for him in a disbelieving tone. He looked offended. Flowey shrank back against Frisk.

“Flowey…” Toriel said warningly, eyes narrowing.

“What?!” the angry houseplant demanded, but he did no more than glare and pout as Toriel and the two humans sat down at the table.

“S-so… there's t-two Frisks and two Floweys?” Flowey broached from Frisk's shoulder, eying his fellow flower warily. Frisk stopped the trickle of tears; attempted murder was looking pretty unlikely, after all.

“Obviously, you _idiot_.” his fellow flower snarled. Flowey gulped, eying them warily.

“Flowey! Enough!” Toriel snapped. “It would seem so.” she said to Frisk, raising her eyebrows. “This town is simply called Ebott. Does that sound familiar to you?” she asked.

Frisk nodded. “Y-yeah… that's the name of our town. But it doesn't look like this.” they said haltingly. “The houses are all different. A-and we know a different Toriel, too.”

“Really?” Toriel said, sounding very intrigued. “Would you tell us more about your home, or your friends? That may help us figure out what is going on here.”

Frisk frowned, and exhaled audibly. “O-okay. Well, there's Papyrus and Sans- they're brothers-” They noticed that the other human was nodding. “Oh. Okay. Uh, we're also friends with Undyne, and Alphys, now, and Mettaton and Napstablook are around a lot…”

“What about Asgore?” the other human, who was sitting next to them, piped up.

“We know him.” Flowey said quickly. “But he's not really a _friend_.”

Toriel let out an unsurprised “Hrmph”. The other human ignored that.

“Those are my friends' names.” they said. “So, did you befriend everyone in your Underground, too?”

Frisk was somewhat taken aback for a moment. “Uh, yeah. …They weren't very nice, at first,”

They saw Toriel raise an eyebrow at that, and hurriedly added “-but we're all friends now! Things are pretty good.”

The other human nodded approvingly. “Nice.” they said, raising up their hand. Frisk blinked in surprise, and their doppelganger waited patiently until they high-fived them. Well, whoever these weird lookalikes were, they weren't too bad.

**Notes for the Chapter:**

> What suffices for plot will probably proceed slowly in this story, because there's so many characters and conversations to get through, what with so many people crossing over and getting displaced.
> 
> Right now, Sans, Papyrus, and Undyne from Undertale are still in Underfell, while Frisk and Flowey from Underfell are in the world of Undertale. Everyone else is in their proper universe.
> 
> Chapter 3 will be up on Wednesday.


	3. Chapter 3

**Summary for the Chapter:**

> Papyrus and Sans try to see if they can learn anything about what's going on; meanwhile, oil and water continue to mix poorly.

**Notes for the Chapter:**

> Featuring a brief, and perhaps somewhat obscure, MST3K homage.

The sounds of the fight continued unabated.

“SHOULD WE SEE WHAT THAT IS???” Papyrus asked. Sans gave him a nonplussed look. “IT'S JUST, I THOUGHT MAYBE SOMEONE IN THIS WORLD MIGHT KNOW WHAT TO DO-”

Sans frowned. “i dunno, bro. they sound more hurtful than helpful.” he said. With no way of knowing when the next reset would be, he was not going to do anything that might endanger his brother.

Papyrus fidgeted. “I KNOW, BUT THEY SEEM TO BE THE ONLY OTHER PEOPLE AROUND! WE CAN AT LEAST SEE WHAT'S GOING ON…” he offered.

The shorter skeleton sighed. He was tempted to take a shortcut, but didn't know what might happen if he did; besides, he didn't want to risk crossing back over without Papyrus.

“okay. but let's try to keep outta sight; don't want 'em to decide they have a _bone_ to pick with us.” Sans said with a wink.

His brother rolled his sockets (in a manner of speaking), and the two of them cautiously crept around the house to look down the other street, proceeding slowly, keeping close to the walls, and out of sight.

The belligerent monsters were only a house down the street, exchanging bullets with gusto. There were two of them, a tall blue monster with a long, wild red hair loosely held in ponytail wearing ragged black clothes, and an almost equally tall skeleton in black and red. It was clear that neither of them had terribly precise control over their magic, as their bullets generally went a mile wide of their target. The blue monster was somewhat worse in that regard than the skeleton.

“HEY! THAT'S MY EVIL TWIN!” Papyrus said, as the brothers looked around the corner. “AND THAT MUST BE UNDYNE'S EVIL TWIN!”

Sans found himself wondering if _his_ counterpart was nearby. His last in-person meeting with the other skeleton had not been a pleasant one, and although he'd seemed much improved when they'd talked in the meantime, Sans couldn't help but speculate about his questions about fighting Frisk.

A light blue spear, crackling with magical energy, flew into the ground only a few feet away from them, impaling itself halfway into the ground. Papyrus jumped involuntarily, bumping into Sans and knocking him out into the open. When the edgier skeleton saw this, he immediately flipped out.

“UNDYNE! STOP!!!” he roared, pointing frantically towards the house. “SANS!”

The fish monster stopped summoning her spears, although the few that had already manifested continued on in their trajectory. She looked down the street where the edgy skeleton was pointing, and her eyes widened in shock.

“OHMYGOSH!! MY BAD!” she shouted.

“SANS, YOU SKULKER, WHAT ARE YOU-” the other skeleton began as he strode toward the house, but then Papyrus left the cover of the wall.

The edgy skeleton stopped dead in his tracks not far from them. They stared at each other for a moment. Then, the black-and-red skeleton covered his face with his hands and complained, “OH NO, NOT _AGAIN_!!!”

“Again?” Undyne's lookalike said disbelievingly, eye widening. “This has happened _before_?! Who are these guys?”

“shortcut went to the wrong place, i think.” Sans said with a shrug.

It is not technically possible for skeletons to go pale at the mention of anything, but if they could, that is what the edgier Papyrus would have done at that moment.

“SHORTCUT?! THIS IS CAUSED BY SHORTCUTS?!” he asked, appalled.

“But what IS 'this'?” Undyne demanded. She waved a hand in the other skeletons' direction. “What… who are _they_? Why do they look like you and Sans? …Are you related?”

“I WAS WONDERING THAT MYSELF.” Papyrus chimed in. “DO EVIL TWINS COUNT AS ACTUAL TWINS???”

“Evil…?” Undyne asked. She glanced down at her outfit. “It's not the best look, but it's _our_ look! I don't go to your house and tell you how to dress yourself! Speaking of which, where IS your house?!”

“UM.” Papyrus's not-so-evil twin cleared his throat. “IT'S NOT JUST THE CLOTHES… THE LAST TIME WE MET WAS BEFORE THE BARRIER FELL.”

The fish monster raised an eyebrow and made a face. “Ah. Awkward.”

“WE'RE FROM ANOTHER WORLD!” Papyrus said helpfully. “RIGHT, SANS?”

“yep. and i don't know about you,” Sans's grin grew wider. “but i'm feeling pretty _cross over_ all this.”

The Papyri both rolled their eyes; Papyrus moaned “SAAANS!” while his counterpart groaned and smacked his palm against his forehead. Undyne's lookalike just snickered.

“So _basically_ , you come from a different world where everyone wears brighter colors, you 'took a shortcut' and came here instead, and now you're stuck here, and we don't know where our Sans is?” she said.

She sighed and bit her lip. Her eye narrowed. “We should probably tell Toriel…” she said with a huff, and exchanged a glance with the edgier Papyrus, who made a face. “…but after that fight with Sans… hey, it's not like anyone else is going anywhere, right?”

Sans shrugged nonchalantly, although what Undyne's lookalike just said was putting him on edge. “heck if i know. it seems to be a random thing. and, uh, fight?”

Undyne opened her mouth to go on, but suddenly a dazzlingly bright beam shot out of the house they were standing in front of and engulfed the edgier Papyrus. When the light cleared he was still standing, albeit somewhat charred, and infinitely more furious. A few wisps of smoke drifted away from him.

“ALPHYS, YOU ABHORRENT ADDLEPATE!!!” he roared at the house. “WHAT THE HECK WAS THAT FOR?!”

Maniacal cackling emanated from the house, and a yellow lizard-like monster emerged in an upper-story window. She was wearing a black labcoat and swirly glasses, and was toting a massive ray gun. The end of it was giving off steam.

“Hahaha! Just testing out my new death ray!” Alphys shouted down when her fiendish laughter began to wind down. “I built it to be a defense mechanism, and then I saw you walking around down there- haha- and just HAD to test it!”

She burst out into fresh peals of laughter, and Undyne guffawed uproariously along with her girlfriend, but Sans and Papyrus exchanged nervous looks.

Alphys's laughter cut off abruptly when she noticed them. “Hey, who are they?” she asked.

“So, this isn't your fault?” Undyne's lookalike said.

The reptilian mad scientist rolled her eyes (not that anyone could see it behind her spectacles). “I think I would've been the first to know if I'd cloned Papyrus and Sans!” she called. “One sec, I'll be right down!”

“does this happen a lot around here?” Sans asked his brother's counterpart, who crossed his arms and nodded grumpily.

 

“um.” began the other Sans, who was starting to sweat under the gaze of Undyne herself. His mouth felt dry, or whatever the appropriate equivalent was for skeletons. “attacked?”

“You didn't see it??” Undyne said. “One minute, I was just jogging along out here, and the next minute it felt like something was trying to turn me inside-out! And now everything looks completely different!”

Sans grinned tightly, and had to keep himself from gulping nervously. “w-what are you asking me for? why should i know?!” he asked in what he thought was a defensive tone.

Undyne, however, seemed to find it offensive. Her eye narrowed even further, and she curled her lip, showing her many large and shark-like teeth. She glared at him with watchful suspicion, single eye roaming from his black-and-red outfit to his own sharp teeth.

“Who ARE you?” she asked brusquely. Her fist clenched even more tightly around her spear. “You're not Sans! Where is he? What did you do to him?!”

Sans took a few steps back out of fear. It was almost certainly because of him that this Undyne had been forced into this world, but with the way she was carrying on there was no way he was going to let her know that it was his fault.

“i don't fricking know!” he snapped, baring his sharpened teeth. “back off!”

Sans mentally kicked himself for slipping into his old habits. Acting aggressive when he was getting anxious had worked back in the Underground, where it had been the best way to get enemies to back off. But this was the surface, he couldn't blast people to make them go away anymore, and this monster didn't know about Sans's old reputation.

That, and Frisk seemed to think all of it was rude; they were a fairly good judge of these things.

But the damage was already done. Undyne had him pegged as a villain- to be fair, he certainly still looked the part- and took his actions to be those of a culprit trying to get away, and not as a fearful retreat.

“STAY RIGHT THERE!” she shouted angrily. “I don't know who you are, but until I find out what happened to my friend, YOU'RE NOT GOING ANYWHERE!!”

Before he could put too much distance between them, Undyne tossed her spear over Sans's head in an arc. It impaled itself in the ground directly behind him, making him jump. A bolt of cold terror lanced up Sans's spine, and out of instinct he summoned up a cage of blue bones around the fish-monster as his left socket filled up with blood-red light.

He cringed. This was going swimmingly.

**Notes for the Chapter:**

> The first half of this chapter was pretty fun to write- especially Alfels's introduction- but the latter half was trickier. The Felsans and Undyne sections in general have been kinda hard, actually, because I have to strike a balance between Felsans being abrasive and being anxious.  
> Undyne's been watching way too much anime.
> 
> There were no crossovers in this chapter, so everyone's still stuck in the same universe as they were in the last one.
> 
> I'll be posting Chapter 4 on Sunday.


	4. Chapter 4

**Summary for the Chapter:**

> Alphys is called in to see if she can make anything of the mysterious case of the double Frisks, while in the world of Underfell Undyne and Felsans's fight continues.

Meanwhile, at Alphys's house in the far less edgy world, the lizard-like monster was working on a project far less violent than a “defense” ray. The world's one and only robotic superstar had just arrived back in town after a long tour, and had popped by Alphys's place. Partly because she was a dear friend that he hadn't seen in a while, but also because he'd undergone some wear on the road and needed her to fix it. Napstablook was there, too, because Mettaton wanted to get them out of their house, even if it was just to go to someone else's.

The scientist had just about finished when the Mew Mew Kissy Cutie theme began blaring in her workshop, startling everyone. Alphys quickly set down her tools.

“S-sorry, sorry!” she said as she rummaged about in her pocket for her cellphone.

“ALPHYS, DARLING, DON'T YOU THINK IT'S TIME FOR A CHANGE OF RINGTONE?” the rectangular celebrity drawled. Now that he wasn't being fixed up, he adopted a more reclining position, out of habit. “YOU'VE HAD… _THAT_ FOR AS LONG AS I CAN REMEMBER.”

Alphys ignored him. “H-hello?” she said.

“Greetings, Alphys.” Toriel's voice answered. “Something quite strange has just occurred, and I was hoping that you would help us to sort it out.”

“W-what is it, T-toriel?” the scientist asked.

Napstablook, whose expression was dispirited by default, somehow managed to look even more downcast, and they floated slowly toward the ground. “toriel…? oh… we're not interrupting something important… are we…?

Mettaton pushed himself up into a sitting position. “TORIEL? SHE COULDN'T JUST WALK A FEW DOORS DOWN AND KNOCK?” he commented.

Alphys gave him a tight-lipped glare before returning her attention to her phone.

“Well,” Toriel began. “there really is no better way to explain this… but a human who looks very much like Frisk just knocked on my door. They say that their name is Frisk also, and they have a talking flower just like Flowey with them. They do not know how they got here, poor child. Have you ever heard of anything like this happening?”

The scientist blinked in surprise. “What?” she said blankly. “Uhh, n-no, I haven't, b-but I can certainly t-take a look! I'll b-be there in just a minute.”

“All right. See you soon.” Toriel said, before hanging up.

Mettaton jumped off of the work bench. “SO, DARLING, WHAT WAS ALL THAT ABOUT?” he asked.

Alphys frowned. “Uhh… I'm not really sure. Something about a human that looks like Frisk?”

“WHAT.” In spite of having a face more akin to a calculator than a real face, Mettaton managed to convey flat surprise, disbelief, and bewilderment, all in one look. “WELL, GUESS WE'LL HAVE TO FIND OUT!” he announced.

“we…?” Napstablook asked from where they were laying on the floor.

“Y-yeah, you don't have to come-” Alphys began.

“OF COURSE 'WE', DARLING!” Mettaton declared. “SOMETHING VERY INTERESTING IS AFOOT, AND I WANT TO FIND OUT WHAT!”

 

At Toriel's house, the human named Frisk wearing the red sweater with black stripes was still sitting at the table, sipping on some apple juice and looking around the room. It was eerie, how similar it was to their own house, although it was brighter, and overall more… whimsical, perhaps. They couldn't quite put their finger on the difference.

Eventually, there came the sound of someone hurriedly, but quietly, tapping on the door. Before Toriel could reach it to answer it, there came another, much louder knock, theatrically rapping out a familiar tune. Frisk smiled at the sound. It seemed that Mettaton was a drama king in both worlds.

“NO NEED TO BE SO SHY, DARLING!” the boxy robot was saying as Toriel opened the door. “MAKE YOUR WONDERFUL PRESENCE KNOWN!”

The boss monster's eyes widened slightly in surprise at the sight of the robot and ghost waiting at her door, but smiled pleasantly and welcomed them in.

“Greetings!” she said. “I must admit, I was not expecting to see you today, Mettaton. And Napstablook, how are you?”

Napstablook looked taken aback at the mention of their name.

“oh… okay i guess…” they said. They seemed more timid than the Napstablook Frisk knew, and were white, rather than light gray.

“S-so, Toriel, what's g-going- oh, is that th-them?” Alphys said, peering around Toriel at the humans and flowers sitting at the round table.

“Wow… you really d-do look alike!” she remarked. Then her eyes widened. “Uhh, h-hello!” she added hastily. “W-what can I do?”

Toriel picked up the potted Flowey from the table, and set him down on a nearby countertop. Mettaton drew up a chair for himself at the table before Toriel took a seat. Alphys hesitantly sat down at the closest chair, and Napstablook hovered over another one. All of them looked surprised to see Flowey on Frisk's shoulder, but made no comment. The second golden flower made angry, distorted faces at the boss monster behind her back; Frisk's lookalike gave him an unhappy look, and he stopped with obvious reluctance.

Frisk was again bemused by the differences between these monsters and their friends back… wherever their friends were. Mettaton's body was smaller, had only one pair of arms, and was seemingly designed with only one ghostly occupant in mind. He was just as dramatic as the Mettaton they knew, but seemed more self-possessed. This Alphys, meanwhile, was even more different. Her anxiety reminded Frisk more of Sans than the mad scientist they knew and… were good friends with, although their friend Alphys had definitely shown a more nervous side over the past year, as she tried to turn her practices around.

What was going on here?

“W-well, um, do you know how you got here?” the anxious Alphys asked them. She withdrew a pencil and notepad from the pockets of her white labcoat.

Frisk shook their head. “Not, I don't.”

“Hmm. How did your day start?” she asked.

Frisk shrugged. “Uh, normal?” they said. The day hadn't been entirely normal- it wasn't every day Toriel was that mad at Sans- but that didn't seem like the kind of abnormal this Alphys was looking for.

“Do you know _when_ you got here?” the lizard scientist went on.

“Ten or fifteen minutes ago, I think.” Frisk said, after pondering the question for a minute.

Flowey cleared his throat. “One minute, we were standing outside our house, and then… everything looked different.” he said. “It felt… pretty weird. I don't really know how to describe it. Sorry.”

Frisk shrugged. “Basically.”

Alphys frowned, and tapped her pencil on the table as she thought. “Hmm. Sounds like s-something to do with space-time, t-to put it simply. I h-heard theories about other universes, b-but didn't think it was practically provable…”

Toriel politely cleared her throat. “You can help them get back, can you not?” she asked.

“I c-certainly hope so.” Alphys said. “But first, I'm going to call Sans.”

Frisk leaned forward in their seat and raised their eyebrows. If everyone was so different, what would the skeleton brothers be like in this world? Toriel and Mettaton, however, simply looked surprised by this.

“SANS? WHAT FOR?” the robot asked.

“Oh! I nearly forgot- he and Papyrus were going to come over here today. Perhaps you do not have to call.” Toriel said.

Frisk's lookalike frowned, and looked slightly worried. “They were supposed to be here… fifteen minutes ago, Mom.” they said, and gestured at Frisk and Flowey. “But they showed up instead.”

Alphys raised her eyebrows, and her mouth settled into a thin line. “Hmm. I'll definitely try c-calling him, then. He might be able to help. He's got his shortcuts, after all, whatever those are.”

She pulled her phone out of her pocket, and started dialing.

 

“COWARD!” Undyne accused as she paced around her cage.

A pool of pale blue magic formed at Sans's feet, and he quickly sidestepped to avoid being impaled upon the spear that shot up from it. If space wasn't misbehaving he would've teleported away before things could have even escalated that far. Undyne snarled with frustration, and formed another spear in her hands. She cast him a furious look, and glanced at the bars with a calculating gleam in her eye. Blue magic or no, it was clear to Sans that she was willing to charge through the bullets to get at him.

Sans drew in a breath, and willed his magic to calm down.

“wait!” he cried out, trying to stop his teeth from chattering. He'd gained plenty of experience in hiding his fear from people over the years Underground, and he drew on every ounce of it. “nothing happened to your friend. this… ugh, where do i even begin…”

Undyne stopped pacing and crossed her arms, glaring at him. Sans forced himself to take a deep breath. Now that she'd stopped preparing attacks to throw at him, he let the bullets dissipate. The fish monster strode toward him, and he flinched away, taking another step back.

“this. well. was probably m-my fault.” he began, tugging nervously at his collar. Anxiety burned in his ribcage as Undyne's angry frown deepened. “i didn't mean it, i swear!”

“Well, what happened?!” the fish monster asked, exasperated.

“i t-took a shortcut-” _No_ , he told himself, he was not going to have an anxiety attack in front of a furious stranger! “it got screwed up, somehow- w-wound up in your world-”

“ _My_ world?? Then what's this supposed to be?!” Undyne interjected, eye flying wide open in an expression of intense vexation.

“my world. keep up.” Sans snapped. The fish monster's eye flashed with anger. "er, sorry. anyway. this sorta happened before, 'bout a year ago- the sans _you_ know crossed over here. he, uh, d-displaced my brother. we all got back in the end, but... now it's happening again.”

“Why didn't you say so before?”

Sans ducked his head. _because you're fricking terrifying_ , he thought. “well... it _is_  kinda my fault, and i'd rather n-not piss off someone who stabs first and asks q-questions later.”

“What did you say, punk?!” Undyne growled.

Sans's sockets narrowed. “you did just try to kill me.” he said.

“'cuz you were acting really shady!” she protested. “And I didn't know about this- world thing! I, uh, thought you were some kind of weird demon that just happened to look like Sans!”

The skeleton gave her an unimpressed look.

“so your alphys watches anime too, huh?” he asked.

“Yeah…” Undyne said awkwardly. She kicked idly at a pebble on the asphalt road. “Uh, sorry for trying to skewer you. And, uh, jumping to conclusions.”

Sans shrugged. Their skirmish had been harrowing, but he'd had worse near-death experiences. “eh. s-sorry for being unhelpful, and… escalating things.” he said.

They stood about awkwardly for a moment, glancing everywhere but at each other.

“how 'bout we never speak of this again?” Sans suggested.

“FINE BY ME!” Undyne shouted.

She started off down the street at a brisk pace, Sans hurrying to catch up with her. In a matter of minutes they drew near to Alphys and the other Undyne's home. Sans had to pause to catch his breath. He could see his brother standing outside the house, thank goodness; he looked a bit singed and more than a bit pissed off, but otherwise fine. The Undyne he was friends with was trying to stifle a laugh, and…

Sans groaned inwardly. The two skeletons from the other world were there, too.

Suddenly, his phone began ringing. Sans fished it out of his pocket and checked to see who it was. For whatever reason, Alphys was calling him.

“hello?” he said.

“H-hey, S-sans!” Alphys said; she sounded much more nervous than usual. That, and she stuttered as much as he did. “Uhh, things are k-kinda weird over here??? I th-thought you m-might want be able to help f-figure out what's going on, y-you s-see…”

Ahead of him, he saw Alphys stepping out of her house, nary a cellphone in sight. Sans restrained a sigh. This day was going to be the death of him. “wrong sans. try again.” he said, and hung up.

**Notes for the Chapter:**

> This chapter wound up being unusually long, but oh well.  
> As a side-note, if UF!Napstablook is light gray rather than white, UF!Hapstablook is bright scarlet rather than pink.  
> Introducing Mettaton into the story was a lot of fun, because of how snarky he is.
> 
> As in Chapter 3, the Sans, Papyrus, and Undyne from Undertale are trapped in Underfell, meeting with Felsans, Felpyrus, UFdyne, and Alfels. The Frisk and Flowey from Underfell are still in Undertale. Everyone else is in their proper universe at the moment.
> 
> I had to go and change the ending of this chapter somewhat; filling in a future plot hole and all that jazz.
> 
> Chapter 5, which was a lot harder to write, will be uploaded on Thursday.


	5. Chapter 5

**Summary for the Chapter:**

> Now that everyone's in one place, the Underfell monsters decide to pass the buck and let their beleagured Queen handle the problem.

**Notes for the Chapter:**

> This one begins with Felsans's POV.  
> Generally, if I say a character is "black-clad" it means they're the Underfell version; while UT!Undyne usually wears black herself, for the sake of this fic and clarity she's wearing white sweat clothes at the moment.

When his brother saw him trudging down the street, Papyrus did a double-take, before adopting an expression of exaggerated annoyance.

“SANS!!! YOU SHIFTLESS TRUANT! WHERE HAVE YOU BEEN?!” he shouted. His not-so-evil twin's sockets widened with shock, and Sans's own counterpart, who was clutching a bag of groceries, raised a brow ridge.

Sans rolled his eyes. “get off my case, knuckle-dragger.”

“USELESS LOUNGER!”

“bonehead.” Sans's grin widened; his brother rolled his eyes, at which their counterparts relaxed. Papyrus's reactions to Sans's puns over the past year hadn't been as irked, falsely or not, as they'd been back when they were Underground, for whatever reason. As far as Sans could tell, he still felt guilty about how he'd been for… basically forever, and was trying to make up for it.

“SERIOUSLY, WHAT HAPPENED?” Papyrus said.

Sans and the Undyne that he'd been walking with exchanged a glance.

“nothing.” Sans said through clenched teeth.

“Nothing!” that Undyne chimed in, a bit too quickly. Papyrus frowned at them, but before he could investigate any further, she turned to the far-from-edgy pair of skeletons and changed the subject.

“Sans! You're all r- Papyrus?! What are you doing here?” she exclaimed.

“we're trying to figure that out.” Sans's counterpart said nonchalantly. He gave Undyne a sideways glance. “there's something _fishy_ about all this.”

When the two Undynes caught sight of each other, they stared at each other in clear shock. The one Sans had been walking with gripped her spear tightly, while his more-or-less-friend held one of her own close to her.

“There's a way to get us all back… right?” asked the Undyne from the friendlier world.

Sans glanced at his counterpart, who gave a half-hearted shrug. That Undyne heaved an exasperated sigh, and cast them both an annoyed look.

“So, have you informed Toriel about this yet?” Alphys asked. She'd made a beeline for the skeletal new arrivals as soon as she'd left her house, and when the extra Undyne noticed Alphys her eye widened. The fish monster looked on at Alphys as she got to work, a mixture of recognition and surprise on her face, while the Undyne Sans knew watched her counterpart warily. Eventually, the extra Undyne shook her head and returned her attention to the conversation, clearly feeling in over her head.

The lizard-like scientist cast an analytical eye over three doppelgangers, and took a notepad and pencil out of her pockets. She looked them up and down, glancing at their counterparts as she did so to take note of the similarities, and scribbled her observations in her notes. Then, much to Sans's embarrassment, she went up to his counterpart and started poking his shoulder, as if making sure he was really there and not some sort of hallucination.

The other Sans looked at her incredulously. “do you mind?” he said, swatting her hand away.

Alphys ignored that, and scrawled something else on the notepad. “This seems like the kind of thing Toriel would want to know about. Parallel universes and all. That's a pretty big deal.” she said warningly. The lizard-like monster turned her attention to the more cheerful Papyrus, but Sans's counterpart sidestepped in front of him before she could start anything.

“HRMPH. WE WERE GOING TO TELL HER.” Papyrus said. “EVENTUALLY.”

Alphys snorted. “If you ask me-”

“WE DIDN'T.” Papyrus grumbled.

“Shut up. If you ask me, you'd better tell her soon, or she'll be even madder at you when she does find out.” the scientist cautioned.

Papyrus's counterpart frowned, as if he'd just thought of something confusing. “WHAT ABOUT ASGORE?” he piped up.

The four denizens of that universe looked at each other.

“Well.” Alphys said, biting her lip.

“Ehh???” Undyne said with a shrug.

“WHAT ABOUT HIM???”

“…he doesn't do much.” Sans explained; their doppelgangers were looking pretty confused. “tori kicked him out of power a year back. remember how things were when you last came here?”

His lookalike nodded, looking serious (well, perhaps not to the casual observer, but Sans knew his own face pretty well).

“yeah. that was pretty much all his fault.” Sans said. His counterpart's sockets widened slightly. “we don't have much to do with him. 'cept when we need a scape _goat_.”

“heh. nice.” Sans's counterpart said, although he didn't look too amused.

“OH. OKAY.” the friendlier Papyrus said. He seemed slightly perturbed, but didn't go on.

Alphys looked at her wrist, where her watch would have been, if she had one. “You going to sit here blabbing all day? Go tell Toriel! And make it quick, I want to have as much time as possible to thoroughly study you all when you get back! I'm expecting Mettaton later, so I've got a bit of a time crunch today.” she said.

“Uh, babe?” the black-clad Undyne said, grinning nervously. Her counterpart raised an eyebrow, and a small smile crossed her face.

“What?”

Undyne nodded her head at their lookalikes. Alphys frowned, and then realization lit up in her eyes. “Oh! Was that-?” she said, holding her hands up to her face. “ _Great_. Uh, I d-didn't mean anything w-weird by that just want to understand all this y'knowwhatI'mjustgonnagoBYE…”

With that, she bustled back into her house.

“welp. guess we better get this over with.” Sans's counterpart said lightly.

“FOLLOW US!” Papyrus said authoritatively, as he and Undyne began leading the other-worlders away.

Sans, meanwhile, stayed back and watched them go. He was really not in the mood for seeing any more of Toriel that day.

 

The Queen of All Monsters was really not in the mood for seeing any more of Sans that day. Toriel holed herself up in her house for the day, figuring she could deal with that issue later. She was sitting at her kitchen table, poring over some paperwork- mostly agreements, disputes, or compromises with the humans, along with a new petition against the snowball tax- and sipping at some coffee. It wasn't particularly her favorite beverage, but at least it wasn't tea. _Anything_ before tea.

Suddenly, her work was interrupted by four loud knocks on the door. Toriel sighed long-sufferingly and set down her coffee. She remained where she was, and ground her teeth for a moment. That was Papyrus's knock.

He was probably there to talk to her about his brother, Toriel determined. Well, if he thought she was going to let this matter drop that easily, he had another thing coming. Especially since they'd kept it under wraps for so long. Really, how did they think she'd react when she found out? Toriel pinched the bridge of her nose, and finally made herself get up and answer the door.

Papyrus was there, all right- twice, to be exact, along with two Undynes and a Sans wearing a blue hoodie. Toriel slammed the door in shock at the sight. It was too early in the day for such nonsense. She closed her eyes, clenched her teeth, and took a deep breath before opening it again.

“Greetings.” she said evenly, for the strangers' sake. “I take it you're here to explain… whatever this is?”

“We would, if we understood it!” Undyne said with a toothy grin. “They just sorta showed up, so!”

“WE ASSUMED YOU'D WANT TO HEAR ABOUT IT.” Papyrus added. “CONSIDERING THAT YOU DETEST NOT BEING NOTIFIED ABOUT THINGS THE VERY INSTANT THEY HAPPEN.”

Undyne's grin tightened, and her eye widened. She looked at the ground, while behind her the other three monsters looked very confused.

Toriel inwardly counted to ten. “Thank you. Papyrus.” she said with forced politeness. Then, she ordered, “Have a nice day.”

She waved Papyrus and Undyne aside, so she could address the newcomers. “Please, come in. I imagine all this must be very overwhelming.”

 _It certainly is for me_ , she thought as she ushered them inside, pointedly ignoring Papyrus's pointed glares.

 

While the Sans from the friendlier world was somewhat wary- he hadn't yet been able to discern if this Toriel liked bad jokes or not, after all- his brother accepted the invitation immediately, followed closely by an intrigued Undyne. This Toriel, the blue-clad skeleton thought, seemed more normal than the other inhabitants of this world. She didn't seem like a villain in the slightest, even a reforming one; just someone who had to put up with a whole kingdom of them.

She wore a formal black dress, with white embroidery, and the Delta Rune emblazoned in red. In spite of the official appearance this gave the gown, it looked more like mourning attire than something one might wear about the house. Sans couldn't tell if it genuinely was a mourning dress- which, considering something terrible had evidently happened in this world's past that Asgore was involved in, along with their counterpart's violent tendencies the last time they'd met, would make a lot of sense- or if she was just wearing it to match everyone else's look.

“I hope they did not bother you.” Toriel said. “Most of the time, I do not feel like a Queen so much as I do a mother with a thousand badly-behaved children.”

Undyne laughed at that.

“If I may ask, who _are_ you?” the Queen asked.

“I AM PAPYRUS, YOUR MAJESTY!” Papyrus announced. He went on to introduce the others and explain what little he knew of the crossovers, while the other Toriel listened closely.

Suddenly, Sans heard shouting coming from outside.

“SANS!!!” Papyrus's counterpart called out, at the same time as Undyne's counterpart yelled “Where'd he go?!”

The Queen of All Monsters rolled her eyes and got up from the table. “I suppose I'd better see what that's all about.” she muttered exasperatedly as she headed toward the door. The other three monsters, curious, followed in her wake.

Outside, Papyrus's evil twin rushed down the street, and skidded to a stop where Sans's doppelgänger had last been standing. He stomped angrily at the street, fists clenched.

“COULD THIS DAY GET ANY WORSE?!” he demanded.

“Eh, I'll bet he's fine.” Undyne's counterpart commented. “No one's died in a crossover yet.”

**Notes for the Chapter:**

> For some reason this one was fiendishly difficult to write, although planning out the conversation with Torifel was pretty fun.
> 
> Made a few adjustments to the way I referred to the Underfell characters, so hopefully things are less confusing now.
> 
> Currently, Papyrus, Sans, and Undyne are stuck in Underfell; UF!Frisk and UF!Flowey are in Undertale, and were just joined by Felsans. Everyone else is in the right universe for now.
> 
> I'll upload Chapter 6 on Monday.


	6. Chapter 6

**Summary for the Chapter:**

> Another pair of crossovers occur, and the day's events take another turn for the worse.

**Notes for the Chapter:**

> Starts from Felsans's POV, more or less, showing the events of what happened outside leading up to the end of last chapter.

Sans, alone on the street, angrily aimed a kick at some rocks on the sidewalk. Sure, they'd stopped trying to kill each other over nothing now that they were at the surface, but they hadn't stopped getting disproportionately angry over it. _The more things change, the more things stayed the same_ , he thought- and then immediately wished he hadn't. It only made the possibility that this shiny new timeline would get reset like all the rest pop into his mind. This really was just one of those days.

Scarcely a minute passed before his brother and Undyne stormed away from Toriel's house. Papyrus had his arms crossed over his chest, and was glaring at nothing in particular as he fumed, and as Undyne walked she heaved an exasperated sigh- both of them looking as irritable as Sans felt. No one was enjoying this most recent feud.

“WHAT DO YOU THINK SHE'LL DO TO THEM?” his brother asked Undyne. “IT'S NOT LIKE SHE CAN SEND THEM BACK.”

Undyne shrugged. “Pfft. Probably talk smack about us behind our backs.” she said with a roll of her eye.

Papyrus snarled angrily. “SHE THINKS SHE'S SO MUCH BETTER THAN WE ARE.” he seethed. “JUST BECAUSE SHE WALKED OUT ON _EVERYONE_ WHEN ASGORE DECIDED TO RUIN EVERYTHING!!”

Undyne narrowed her eye. “Exactly! I've talked to some guys from the Ruins. Things weren't much better there. They still fought. They still _feared_. And all she really did was yell at Froggits to get off of her lawn.”

“NYEH HEH HEH!” Papyrus cackled at the mental image. “WELL, AT LEAST SHE TAKES CARE OF FRISK.”

Sans snorted. “i dunno. i thought we were… adequate babysitters for a few days there.”

Undyne threw back her head and guffawed loudly. “HAH! After all we did? It's a wonder they're still friends with us!”

The skeleton brothers didn't disagree. They knew, or at least assumed, that Frisk's main motivation in befriending them was to save their own and Flowey's skins. Still, they weren't offended- that was just how things had worked, back then.

“Say, did you see my… me… uh…” Undyne frowned, and looked upwards, as if hoping the sky would tell her what phrase she was looking for. “The _other me_ when you crossed over last time?”

Papyrus shook his head. “THE ONLY DOPPELGANGERS I ENCOUNTERED WERE MY OWN AND SANS'S.”

“So you actually interacted? What happened??” Undyne asked. “Other-Me looks like she'd fit in around here, but they look… soft.”

“I SUPPOSE SHE DOES.” The taller skeleton's scowl deepened. “I FOUGHT AGAINST MY COUNTERPART THE LAST TIME. HE'S STRONGER THAN HE LOOKS.” he admitted. He did not care to share with either of them that he'd failed to frighten Sans's counterpart, who had then punned at him, put him on hold to take a phone call, and thrown him against a wall. Twice.

The shorter skeleton began backing away, so he'd be out of range if bullets started flying. Knowing the two of them, they'd probably restart their fight any second minute now, partly to let off steam, but mostly because they felt like it. Most days, Sans would just stay where he was and just spontaneously go be somewhere else if things got dangerous, but now…

He clenched his fists in his pockets. Murphy's Law was showing off today.

Sans frowned. A piece of paper scratched against his hand, one that he was certain hadn't been there earlier that morning. Had his counterpart put it there? It was probable that the other him was at least as good at manipulating space as Sans was, if not better.

He took the piece of paper out of his pocket. It had been crumpled up and flattened. Carefully, he unfolded it, and saw that something had been written on one side of it.

Sans's sockets went pitch black, and he held the message out at arm's length. Horror seeped into his marrow, and a flood of fear washed over him.

He recognized that handwriting.

Anxiety blazed within him, and across the street his brother and the fish monster reignited their brawl. A spear strayed from the scrappers, landing a few yards short of Sans. Out of habit, before he could stop himself, he disappeared into thin air.

“ _This won't fix anything_.” What the heck was _that_ supposed to mean?!

 

“H-hang on, I'll try again in a s-sec, something's wr-wrong with my phone…” Alphys stuttered, as she frowned at her phone. She hadn't had a chance to try calling Sans back yet. After calling the “wrong one”, she'd been too stunned to call back for a few moments, and when she did try, she was interrupted by a call that apparently came from her own number. Whenever she tried canceling it, she got another one. The lizard-like monster couldn't figure out what was wrong with her phone.

“ARE YOU SURE IT'S MALFUNCTIONING?” Mettaton remarked, drumming his fingers on the table impatiently. “IT IS ONE OF YOUR DESIGNS AFTER ALL, DARLING!”

“W-well, I don't see what else it c-could-”

Alphys cut off mid-sentence when she heard something outside. Her eyes widened.

“Is that-?” Toriel began disbelievingly. In his flowerpot on the table, Flowey burst out laughing. It sounded like swearing. More to the point, it sounded like-

“Sans!” the new Frisk said happily, while the other Flowey looked toward the door hopefully. They pushed their chair away, and gave Toriel a questioning look. She gave a small nod, still shocked by what she'd heard, and they got up and hurried to the door.

Frisk pulled it open, and peeked out, casting an eye over the whole street. Finally, they saw what they were looking for- a rather angry, short skeleton in a black jacket. They waved to get his attention as the other monsters crowded about them to see what was going on.

“Sans! Over here!” they called.

“hey, brat.” Sans called as he walked over, eying the other monsters with veiled wariness. Toriel raised an eyebrow. “so you're stuck here too, huh? well, frick.”

 _Great_ , Sans thought. On top of everything else, now Frisk and Flowey had gotten dragged into this mess, and he had another Toriel to put up with.

“Are y-you the Sans I tried to c-call?” asked a yellow reptile monster in a white lab coat.

Her glasses didn't obscure her eyes, the way her counterpart's did. This Alphys's eyes were wide, and she stood somewhat hunched, twiddling her fingers nervously. Behind her stood a boxy gray robot with a screen for a face and… a pair of long legs with pink boots. It was difficult to tell how he was taking Sans's appearance. His smaller stature and lack of a second pair of arms were rather conspicuous, and Sans caught sight of a white ghost lurking behind the other monsters, somewhat faded and blending in with the background.

There was even a second Frisk, wearing a differently-colored sweater, looking at him with amazement. Curiously, there was no sign of Flowey's double, on this Frisk's shoulder or elsewhere.

Sans felt a twinge of anxiety. These somewhat more colorful people seemed curious, and only mildly suspicious. They didn't look like the sort of folks who'd grown up in a kill-or-be-killed society; the skeleton reasoned he'd have to watch what he said about his own world. No point in making them distrust him anymore than they might already- the swearing, profusion of red and black, and the gold tooth, probably weren't helping matters.

“yep.” Sans said, stopping a few feet from the Frisk he knew. “didja ever reach, uh, other me?”

The probably-a-scientist shook her head. “No.” she said, looking down nervously. “My ph-phone kept acting funny. It said I was tr-trying to call m-myself.”

Sans snorted and rolled his eyes. “pfft. that'll be alphys. she's dying to figure out what's going on.” he said.

This Alphys pulled a paper and notepad from her pocket. She furrowed her brow in thought. “Really? I'm getting a phone call from another universe? How c-can you be sure?”

Sans's grin tightened, and he shoved his hands more deeply into his pockets. “uh, well, that's how it was last time.” he admitted, looking off to the side.

Alphys's eyes widened. “This h-happened before? W-when? H-how did you g-get back?”

Frisk blinked quickly in surprise. “You never told me that!”

Sans fidgeted awkwardly where he stood. It was a troublesome topic to explain, and he didn't entirely understand himself how his counterpart had worked things out in the end, although he had a few hypotheses. “'bout a year ago. before you showed up.” he said. “other sans crossed over somehow. my brother got shunted over here. got back through luck, basically.”

Toriel's eyebrow went even higher. “Sans _and_ Papyrus know about this? Good gracious.” Then, she added, “Would you like to come inside?”

Sans awkwardly accepted the invitation, and the whole crowd of them bustled into the house.

His orbitals widened in mild surprise when he caught sight of the potted flower fuming on the table.

“SURE, run off and leave the flower behind! In case you _idiots_ forgot, I'm stuck here in this pot!” it complained.

Sans raised a brow ridge. Was _Flowey_ the only evil monster in this world, then?

“OH, WE DIDN'T FORGET.” Mettaton said bluntly, heading back to his seat.

But he didn't make it all the way there. With a quiet noise like someone scratching a nail against the fabric of time and space, he vanished, and a short skeleton in a blue jacket holding a bag of groceries instantly took his place. Although his smile was wide, to Sans it looked forced. He was tensed up, and his pupils scarcely more than pinpricks of light, but most significantly, he was alone.

**Notes for the Chapter:**

> I feel like I've gone from a third-person limited narration to third-person omniscient somewhere between A Novel Experience and this fic...  
> Anyway! This one was a heck of a lot more fun to write than Chapter 5; the first half especially practically wrote itself. That, and a thread of the overarching background plot has just revealed itself.  
> At the moment, Papyrus, Undyne, and Mettaton of Undertale are stranded in Underfell. Sans (from Undertale) just went back to his own universe, where Felsans, UF!Frisk, and UF!Flowey are stuck.
> 
> Chapter 7 will be posted on Friday.


	7. Chapter 7

**Summary for the Chapter:**

> Everyone tries to figure out what the heck just happened.

**Notes for the Chapter:**

> Starts out in Undertale, from UT!Sans's point of view, then switches to Underfell.

Sans didn't know what to do.

When it became apparent that his counterpart had crossed over- for the third time in a single hour- he had rushed to get himself, his brother, and Undyne back home as quickly as possible. They'd ducked back inside, Sans had taken a shortcut, and for a brief instant everything seemed to be going wrong properly. His counterpart's own shortcut had set space ringing as expected, and Sans felt the shock of his crossover exploding around him- and then two more powerful shockwaves had thudded into him, one from either side. As he returned to normal space, Papyrus and Undyne were wrenched from his grasp.

He emerged in Toriel's house alone.

The short skeleton still managed to take stock of the situation. Toriel was standing nearby and looking at him with surprise written all over her face. Something had set off Napstablook crying, and a pen fell from Alphys's hand onto the table as she stared in blank shock. There were two Frisks, and a pair of Floweys; a grin full of malicious glee was creeping across the face of one. And, finally, there was his own counterpart, standing only a few feet away, who appeared to be on the verge of an anxiety attack.

All eyes were fixed on Sans.

“what happened?” the other skeleton demanded.

“i dunno.” Sans admitted, as he pulled his phone out of his pocket. It brushed against a crumpled-up piece of paper as he did so- where had that come from?- which he ignored. He had more important things to worry about.

The short skeleton typed in Papyrus's number. There was no way that a signal couldn't get between worlds with space as unstable as it was. Even so, Sans waited with bated breath until the second ring, when his call was picked up.

“SANS! ARE YOU OKAY? WHY DID WE END UP IN DIFFERENT PLACES??? WHY IS METTATON HERE?” his brother asked frantically.

“i'm fine, bro. i, uh, dunno what happened. mettaton…” Sans closed his eyes. “great. this coulda gone better.”

“mettaton… he'll come back… right…?” Napstablook asked miserably.

“I'm sure he will, Napstablook.” Toriel said comfortingly.

“I C — HEA — OU VERY WEL —” Papyrus said in a worried tone. As he spoke, his voice sounded progressively more distant and distorted. It didn't sound exactly like static, or like a normal bad signal; it was the audial equivalent of looking at a jigsaw puzzle as small pieces of it fell out of place. If space was becoming more stable again, Sans would've expected the call to just fade out regularly as the signal's strength weakened. This sounded like something else entirely.

“papyrus? wait, hang on a min-” Sans said, as all noise from Papyrus's end faded away entirely, and the call suddenly dropped. The lights in his counterpart's eyes faded away. “welp. that's not good.”

“Sans- w-what's wrong?” Alphys asked, watching him worriedly. When she blinked, Sans had suddenly gone from standing across the room to being seated next to his counterpart. He plopped the bag of groceries on the table.

Sans let out a sigh. “i tried crossing over with papyrus and undyne, but…” He trailed off, and shrugged. “and now it looks like i can't go back.”

Alphys's eyes flew wide open. “W-wait, Undyne's st-stuck over there t-too?!” she asked. She furrowed her brows determinedly. “If th-there's anything I c-can do, t-tell me! W-what do y-you know? I h-haven't done m-much p-practical research in this f-field, but I read a l-lot on theories ab-bout alternate universes.”

And if Sans had anything to do with it, it was going to stay that way. No need for her to see reports about the anomaly and ask the awkward questions that came with them. He exchanged a brief look with his counterpart, who had slumped into a chair next to the human in red and black, and was tugging nervously at his collar. Sans couldn't wait for the whole disaster of a day to be over.

“it went wrong; dunno how. maybe something interfered… somehow.” Sans finished lamely, feeling a twinge of guilt after seeing how horrified his counterpart looked when he brought the _something_ up. Not for the first or last time, he decided he didn't want or need to know what had happened in the past of the other world. He had enough to worry about already.

The scaly scientist wrote something down, and tapped her pen against the table as she thought. “W-what sort of… s-something?” she asked.

“i don't know, unfortunately.” he said with a shrug. “'s just a hypothesis. felt like papyrus and undyne were pulled away from me, somehow.”

His counterpart's eyes widened. “WHAT?!” he blurted out, before Alphys could keep questioning Sans, and startling the Flowey not stuck in a flowerpot. “how?! but… that's…” He ran a hand over his cranium. “that's never happened before! when did that happen?!”

“while i was partway here.” Sans explained.

Alphys again opened her mouth to ask a question, but the panicking skeleton interrupted before she could begin. “things don't just- just _stop teleporting_ when they're already outta regular space!” he exclaimed.

Sans shrugged again. “i can't explain it either.”

His counterpart's point was worrying and true. Both Sanses, as far as he could tell, possessed powers over space that were many and varied. Most usefully, they could teleport themselves, and others, and objects, and even their own bullets, across long distances. Back in the Underground, Sans had used his abilities to move his one small station building from Snowdin across the whole kingdom, condiments and snow and all, so he could work multiple jobs at once. That was, when he wasn't using them to find comfortable places to slack off or pulling pranks on Papyrus and Frisk. His powers were a layabout's best friend and he abused them shamelessly, although he had occasionally used them for more productive ends, something he suspected his counterpart had been forced to do.

As he put his hands back in his pockets, one of them brushed against that strange piece of paper again. He'd only just noticed it now that he'd re-entered normal time, but wasn't entirely certain that it hadn't been there before. His pockets were like black holes, strictly metaphorically speaking, in that things tended to go in and get lost and never come out again. For all he knew, it was a receipt from months ago for something he'd forgotten about.

Then again, considering the circumstances… Had his counterpart put it there remotely? Sans hadn't seen him writing anything. Then, a thought struck him. If things could be taken or separated from him while he was teleporting, then perhaps things could be planted on him, too.

 

“SANS? ARE YOU THERE?” Papyrus shouted into the receiver, but all that came from the other end was silence, and finally, the call seemed to end itself. Undyne put a comforting hand on his shoulder, while their counterparts watched on unhappily, and Mettaton looked about the room in bafflement as he tried to figure out what the heck had just happened to him. The Queen of All Monsters, meanwhile, was busy clearing away her paperwork.

Papyrus frowned for a moment, which quickly rebounded back to his usual upbeat smile. “WELL! SANS HAS PRANKED PEOPLE ACROSS TIME AND SPACE BEFORE. THIS… ISN'T EXACTLY A PRANK, BUT I'M NOT TOO WORRIED ABOUT HIM!”

His counterpart's scowl deepened as he paced across the room, arms crossed. “HRMPH. I WISH I COULD SAY I SHARED YOUR OPTIMISM.” he grumbled.

Meanwhile, in a corner of the room, Mettaton reached a hand behind his back in an attempt to flip his switch- it is easier, after all, to get the calculated combination of surprise, irritation, and yet also composure that he was going for across to unfamiliar people when one has a face to convey it with. For once he was glad to not be the center of attention, as it meant no one was paying his fumbling efforts any mind.

“IT'S QUITE SIMPLE, ACTUALLY!!” Papyrus said brightly, privately glad for the distraction. “JUST BELIEVE IN YOURSELF! AND IN EVERYONE ELSE!! ALL THE TIME!!!”

The edgier skeleton paused his pacing. “I MEANT IN THIS SITUATION,” he half-lied. “BUT, THANK YOU?”

“NOW-” Across the room, Mettaton finally managed, and quickly pressed on as if nothing had happened. “-Can someone please explain what we're all doing here?”

The edgier Undyne was sitting at the table, resting her head in one hand. She cocked her head in mild surprise when she saw the robot's more humanoid form.

“Huh. You're pinker than our Mettaton.” she observed idly. “And shorter.”

“AND YOU DON'T HAVE THE EXTRA ARMS.” Papyrus's counterpart added tensely, as his pacing resumed.

Mettaton leaned an elbow on the table, and with his other hand impatiently drummed his fingers against it. “Extra arms?” He looked over at Papyrus and Undyne. “Is that a common feature here? I don't know how you can all handle it. Now. As I was saying-”

Before he could get any further, and without so much as a single knock of warning, the front door swung open. Toriel sighed quietly and rubbed at her temple as a short yellow monster in a red dress and menacing black labcoat swept into the room. Following her wake, looming out on the porch, was a tall humanoid being, who had to stoop to make it through the door.

 _This_ Mettaton halted once inside, and looked down at his counterpart, surprise lighting up in all four of his eyes.

**Notes for the Chapter:**

> Not the longest of chapters, but at least it's not the shortest of chapters, either.  
> After so much destabilization and so many crossovers in quick succession, space is getting a bit of a break in this chapter. More will be explained later.
> 
> You know, people always make so much of Sans's shortcuts, but they never address the snow on the roofs of his stations, even the one in Hotland, or how he made a key "already be" on Frisk's keychain without moving. So here I wrote him being able to take items with him, and move things away from him.
> 
> Universal headcount: UT!Papyrus, UT!Undyne, and UT!Mettaton are stuck in Underfell. Felsans, UF!Frisk, and UF!Flowey are stuck in Undertale (Alfels is also talking to them from across universes). Everyone else is in the right place.
> 
> Chapter 8 will be here on Tuesday.


	8. Chapter 8

**Summary for the Chapter:**

> Shenanigans continue unabated.

The two robots stared at each other disbelievingly for a split second; the black-clad Undyne looked on, a smile creeping over her face that indicated she wanted someone to pass her some popcorn.

“Well, well, well, _well_.” the pinker Mettaton said. “I never thought I'd see the day when I met someone as stunning as myself! And I'm guessing those extra arms come in pretty handy!”

His fellow robot smiled gladly, and gracefully stretched out his arms in (what he thought to be) was a striking pose. Well, his upper pair of arms was graceful; the lower pair moved, too, but something about them seemed distinctly half-hearted. At the same time, his upper eyes cast Alphys a sideways glance, while the lower ones continued to stare downwards.

He stood a head taller than his counterpart, with somewhat pointier features and slightly longer “hair”. Rather than pink, he was colored in deep red and yellow. But, of course, the most striking difference were the presence of an extra pair of eyes and arms.

“Is this was you were babbling about, Dr. Alphys?” he said, in a voice that was a touch lower in tone. “You left out the best part! It's always a pleasure to meet someone so handsome… and with such wonderful taste! Some people think these-” The taller robot waved an arm flippantly. “-are a little alarming. And I must say, that pink really suits you.”

Mettaton smiled with pleasure and struck a pose of his own. Behind him, Undyne rolled her eye and the edgier Papyrus skeptically raised a brow ridge.

“Why, thank you! I-”

“Say, why don't you have four arms?” Alphys said, bringing their budding mutual admiration society to a grinding halt. Both Mettatons turned to look at her, affronted.

“I'm trying to figure out this whole 'alternate universe' business.” the mad scientist explained. “Understanding the differences between counterparts seemed like a good way to start. Do you both just use the one pair, or…?”

Mettaton frowned warily. “Both?”

“Dr. Alphys…” his counterpart said warningly.

A look of unpleasant comprehension slowly dawned on the reptilian monster's face. Her eyes widened slightly, and the corners of her mouth fell. She took a step back away from the two robots, then closed her eyes and took a quick breath.

“If you'll excuse me…” she said, glancing around. Seeing nowhere she could really head off to, she made do with an empty corner, pulled her phone out of her pocket, and began quickly dialing on it as if she had a very important phone meeting she couldn't miss.

Toriel, having tidied up the table, began making for the door, then halted halfway to it, with an indecisive expression on her face. After a moment's hesitation she turned and addressed the strange assortment of monsters.

“Frisk left the house not long before this all began.” she explained. “I want to go see if they are nearby. But-”

She fixed the red-and-black monsters with a glare, reserving the longest glare for the edgier skeleton. “-you must all promise to behave yourselves! I do not want to come back to a disaster zone.”

Papyrus's counterpart scowled petulantly. “STOP ACTING LIKE WE'RE CHILDREN!” he complained querulously. “YOU'RE NOT OUR MOTHER!”

“No, I'm your Queen!” Toriel said shaking her head, then left, leaving a fuming skeleton in her wake.

The two fish monsters began laughing their heads off as Papyrus's counterpart sulked. He rounded on them, fists clenched.

“OH, SHUT UP, WILL YOU?!” he snapped at his… “friend”. “YOU WERE COMPLAINING ABOUT HER TOO, FIVE MINUTES AGO!”

Eventually, the Undyne from that world calmed herself down enough to ask, “So what do we do now? C'mon, Papyrus, you're Sans's brother, do you know how he does… whatever the heck it is he's been doing?”

The friendlier skeleton shook his head. “ALAS, NO! SANS… NEVER REALLY TELLS ANYONE ANYTHING. ESPECIALLY NOT ABOUT THAT STUFF.”

“MOST CERTAINLY NOT.” his counterpart added. “HE JUST HAS A KNACK FOR GETTING SPACE TO DO WHAT HE WANTS. OR SOMETHING. I CAN'T THINK OF ANY OTHER WAY HE COULD HAVE BROUGHT THE COUCH BACK, ANYWAY.”

The black-clad fish monster nodded- she had been there when that had happened. She and Papyrus had been arguing in the wreckage of broken chairs, and when she turned around there was suddenly a large green sofa before her, which Sans was napping on.

“So what if Sans is… being Sans?! I bet Alphys will figure it out!!” the other Undyne exclaimed. “She can make anything! Giant anime swords, cellphones that turn into jetpacks, Mettaton…”

The pink robot posed dramatically. “Her crowning accomplishment, if you ask me.” he said.

His counterpart cast a look downwards with both pairs of eyes, fidgeting a bit. Things weren't too bad, now that he could perform like he'd first wanted, instead of just selling weapons, and Alphys had started bending over backwards to do anything he or Napstablook needed to try to make it up to them. And the extra arms were fairly convenient. But still… they'd only been on the surface for a year, and seeing his counterpart looking just the way he'd always dreamed was putting the taller Mettaton in a rueful mood, to say the least. In the corner of the room, Alphys tensed, curling up and aggressively focusing on her cellphone conversation.

“EXACTLY!” the edgier Undyne said enthusiastically, noticing her girlfriend's distress. “After building giant combat mechas and all sorts of crazy awesome energy weapons, how hard could a portal be?”

“Giant combat mechas??” her counterpart asked, taken aback. “Sounds pretty neat… but MY Alphys invented dimensional storage boxes! So basically she's ALREADY invented portals!!”

“Well- my Alphys did that, too!” the black-clad fish monster shouted, glaring at her counterpart.

Meanwhile, the edgier skeleton looked over his shoulder at the kitchen. He furrowed his brows, and hmm'd thoughtfully.

“DARE I?” he wondered aloud. The Undyne he knew looked over at him, eye narrowing. “I DO. I'M GOING TO MAKE SOME SPAGHETTI.”

With that, he began striding towards Toriel's kitchen.

“SPAGHETTI??? CAN I HELP?” the friendlier skeleton asked, getting up to follow.

“Are you _trying_ to piss Toriel off?” the black-clad fish monster asked them. A grin was growing on her face. It was the type of grin most commonly seen on the face of a student who sees a peer about to do something foolish, and is glad that they will not be the one getting in trouble this time. “I can't WAIT to see the look on her face when she gets back!”

“HRMPH. GO BOIL YOUR HEAD.” Papyrus snarled, although the other tall skeleton paused, looking thoughtful.

“Besides, your spaghetti's AWFUL.” Undyne went on loudly, to her counterpart's clear alarm. “I could barely keep it down the first time we tried cooking together…”

“SO YOU'VE SAID. MANY TIMES.” Papyrus said, as he kept going. “YOU ALWAYS FAIL TO MENTION THAT THAT WAS MOSTLY YOUR FAULT.”

“WELL, I'M NOT WORRIED ABOUT THE QUALITY ONE BIT!” his counterpart announced, posing dramatically. Without some wind to make his scarf billow behind him it didn't have quite the gravitas he was going for, but it was sufficient for the occasion. “AFTER ALL, I AM PAPYRUS, UNPARALLELED SPAGETTORE!”

Undyne's counterpart, who had gone stock-still from the moment Undyne first insulted the edgier skeleton's cooking, suddenly laughed. “Yeah! Uh, your cooking skills are great!” she said with feigned enthusiasm.

“YOU WOULD KNOW, YOU TAUGHT ME! NYEH HEH HEH!” the friendlier Papyrus said as he hurried after his counterpart.

Undyne raised an incredulous eyebrow. “ _You_ taught him, and he's good?” she said. “You're kidding me.”

Her counterpart smiled hugely, and her eye flashed with urgency. “Yes! He is!!!” she hissed, gritting her sharklike teeth. The more villainous fish monster glanced over at the friendlier version of Papyrus.

“Well, I'll, uh, take your word for it that he's good!” she said cheerfully, pasting a grin on her own face. “Unlike someone I could mention!”

The edgier skeleton stopped short, and meant to turn and confront Undyne so he could defend himself, and explain just how unlikely it was that his counterpart was any better at cooking than he, if Undyne's counterpart was his teacher, how in Papyrus's opinion just the opposite was far more likely, et cetera; but something made him pause. His counterpart did seem very enthusiastic and proud of his abilities, regardless of what they actually amounted to. If there was a universe out there where a skeleton like him could actually get some respect, people actually supported him- unlike someone _he_ could mention- and was actually able to be that… happy, then he wasn't going to get in the way of its good work.

Reluctantly, he let the insult pass unchallenged, and had to limit himself to giving the fish monster a glare that screamed “REST ASSURED, YOU WILL DIE FOR THIS LATER”.

 

Suddenly, the Mew Mew Kissy Cutie theme started to play, cutting into Sans's hypothesizing about space-time. Toriel, who was sitting next to Alphys and wondering if she should make everyone lunch, was merely bemused by yet _another_ phone call, but the three inhabitants of the other world were all startled by the unfamiliar sound. Napstablook, meanwhile, had faded away entirely.

Alphys glanced down at her phone. “Y-you're sure th-that's the, uhh, other m-me?” she asked Sans's counterpart, who nodded.

With unexpected speed, Alphys picked it up and answered the call, putting it on speaker as she did so. Toriel

“H-hello?” she said.

“Finally! I was wondering if you'd pick up. Hello from another universe.” said the person on the other end, who sounded just like her.

Alphys's eyes widened with excitement. “Ohmygosh, you're ME! Th-this is amazing! Have you figured anything out about… all this?”

Far across the seas of space and time, her counterpart made a sound of intense exasperation. “No. It's _infuriating_!”

Toriel cleared her throat politely. “Greetings, er… Dr. Alphys.” she said. “What _do_ you know about the situation?”

“Toriel? Fascinating…” the other scientist mumbled. “Er, nothing. All I know is that alternate universes exist, and that everyone from your universe- who I've seen- is a counterpart of someone over here. And that this is Sans's fault somehow.”

Sans's counterpart glowered at the table. “get stuffed, alphys.” he snapped, loud enough for the phone to pick it up. The Frisk in red and black patted his shoulder.

“What's your Alphys like?” their blue and purple doppelganger asked quietly, as the two scientists and lone Queen continued to discuss the day's strange events.

“Oh! She's… hmm.” The second human's eyes darted from side to side, and their voice dropped to a whisper. “Do you read many comic books?” they asked.

The first human shook their head. “No, but I've read about them.”

“Fair enough. Alphys is… basically a mad scientist.” the second Frisk explained quietly. “She used to be a full-blown evil supervillain genius.”

The edgier Sans cast a hurried look at Toriel, and the first human's eyebrows flew up.

“Wow!” they said. “Used to be?”

Flowey shrugged, inasmuch as a flower can shrug. “That's… how a lot of people in our world are, actually. They're all nice now,” he added hurriedly and unconvincingly. “but things… used to be really messed up.”

On the table, the other golden flower was straining to overhear the quiet conversation. Anything they were trying to hide _had_ to be more interesting than two Alphys-es fangirling over each others' existence. A spiteful smirk spread across his face.

“What, so you're saying that in your world, it's kill or be killed?” he taunted loudly, drawing the others' attention. “That's the funniest thing I've heard all day.”

“S h u t   u p.” Sans's counterpart growled, slamming a fist on the table. His sockets were dark. “O r   I ' l l   b l a s t   y o u   t o   k i n g d o m   c o m e.”

“You're no fun.” the potted flower whined.

“Flowey! Enough!” Toriel said sternly. “As for you…”

She turned to Sans's counterpart. “I would very much prefer if you did _not_ make death threats under my roof.”

While the golden flower simply sulked, the short skeleton quailed, and gulped nervously. He nodded quickly, and the boss monster returned her attention to mediating the phone call. The conversation was getting heated, as the two Alphys-es had somehow gotten onto the topic of Undyne(s).

“Was your Mettaton a _real_ killer robot?” Frisk asked curiously. “'Cuz the one we have here used to be like that. He was faking it at first, though.”

“Yeah, that… that was basically Mettaton in a nutshell.” the other human replied. “He didn't want to be one, though. It's a long story.”

An expression of surprise crossed Frisk's face. They snickered. “Huh. That's funny. Mettaton was faking it when I met him, and then tried to do it for real.”

The skeleton in a black hoodie was only half-listening to their conversation; he was a bit more preoccupied with keeping a wary socket on Toriel, and with his own anxieties about, well, everything.

“say, you would'nt've happened to put a piece of paper in my pocket, would ya?” Sans suddenly asked him, very quietly.

“no.” his counterpart muttered disdainfully, giving him an 'are-you-crazy' sort of look. “you got one, too? and if you wanna know how, i dunno, you tell me.”

Sans half-shrugged. “your guess is good as mine. if it's the guess i think it is.”

His counterpart sighed, suddenly looking very tired. “great. what does he _want_?” he growled. “first they destabilize space, then they mess with shortcuts, and now… pieces of paper?”

“Papers?” Alphys said suddenly, looking away from her phone call. The two Sans-es stared at her in stunned silence. The lizard-like scientist blinked. “There are s-scientific papers ab-bout this? Do you h-have them?”

The short skeletons glanced at each other, both silently wondering, 'now what?'

**Notes for the Chapter:**

> Why does "spagettore" not have an h in it?! Spaghetti has an h in it...
> 
> Writing Mettaton at the beginning of this chapter took ages. I dunno why, but getting him to feel in-character was seriously uphill work, although the subtle puns were fun. But aside from that, I'm pretty pleased with this chapter.  
> If anyone's wondering, I imagine that Alfels has somewhat different tastes in anime than Alphys.
> 
> For today's interdimensional headcount, UT!Papyrus, UT!Undyne, and UT!Mettaton are stuck in Underfell. Felsans, UF!Frisk, and UF!Flowey are stuck in Undertale. Everyone else is in the right place for now, but Alfels is on the phone with her counterpart at the moment.
> 
> Chapter 9 will be up on Saturday.


	9. Chapter 9

**Summary for the Chapter:**

> In Undertale, the monster try to find a solution for the problem. In Underfell... not so much.

The short skeletons glanced at each other, both wondering, 'now what?'. On the one hand, divulging the existence of the studies and reports- and, if it came to that, the machine- might help speed up getting everyone back to their proper universe. But on the other, doing so would require them to actually explain things. That, and it would lead to even more awkward questions later.Silence hung over the room as they thought, and seemed to hang particularly heavily over Sans and Sans. Seven pairs of eyes watched- and one cell phone listened to- the two of them expectantly (Napstablook had gone back to being slightly visible). Sans's black-clad counterpart cast a nervous sideways glance at him.

“i mean, i'd assume they exist.” Sans lied nonchalantly. He'd helped write or at least assisted with the research on many of those papers himself. “but i've never seen 'em.”

The friendlier flower brightened. “Do you know where they _could_ be?” he asked. “I could go look for them, or something…”

Napstablook hmm'd. “but they'd be in the underground… sorta far away…” they mumbled. Flowey's face fell, and so did the ghost's. “sorry…” they added.

The Frisk in red and black suppressed a giggle at Flowey's dashed plan.

“What?” the flower asked self-consciously. “They can't all be winners.”

“and don't look at me.” the other skeleton said moodily. “i'm not a science guy. 'sides, this isn't even my universe.”

Alphys's face fell. “Oh. Okay.” she said. Then, just before one of the two Sans-es could even inwardly breath a sigh of relief, she frowned. The skeletons braced themselves. “Well… since all th-this is c-connected to your 'sh-shortcuts'… c-could you m-maybe explain how they w-work?” she asked.

“magic.” Sans said simply. Frisk stifled some giggles, and Toriel rolled her eyes.

The boss monster opened her mouth to speak, but before she or anyone else could attempt to extract an actual answer from either Sans, there was a knock at the door.

 

The other skeleton quickly turned his head to see who it was. He was hoping that it was just a random passerby who wanted to complain at Toriel about something, the way they so often did in his world. But he had a nasty feeling that it would be another counterpart, of the someone whom everyone from his world went out of their way to avoid, but didn't seem to have a bad reputation in this one.

“Howdy,” said Asgore Dreemur, ex-King of All Monsters, one of the most powerful monsters in existence, and part-time stuff of Sans's nightmares. He was carrying a brightly-colored plastic watering can, that was ludicrously small in comparison with his massive hand. “I hope I'm not interrupting?”

Sans gritted his teeth as he glared incredulously at the doppelgänger of the monster who had ruined his world. _This_ boss monster tarried patiently and sheepishly at the doorstep, wearing a pastel T-shirt. He didn't look even the least bit intimidating- more like a big fluffy pushover- and the dissonance between him and the Asgore that Sans knew of was extremely jarring.

He glanced at Frisk, whose eyes were wide as Loox's. The human had steered clear of Asgore when they could, even though that now the Barrier was broken there was no way Dreemurr was going to hurt them. But perhaps that was just it; now that they were on the Surface, living with a protective boss monster and fiercely loyal friends, they didn't need to act affectionate to keep people from killing them anymore, and their survival instincts could go back to functioning properly and keeping them away from villainous types.

“Greetings, Dreemur.” Toriel said evenly. Some things weren't that different across universes, Sans supposed. “What brings you here, today?”

Asgore held up the watering can. “Frisk left this at my home yesterday.” he explained. “So I came here to return it.”

“Very well.” the Queen of All Monsters said (wait, was Toriel the Queen in this universe?, Sans wondered).

The human in blue and purple was delighted to see the giant furball. To Sans's surprise, they sprang up from their chair to go hug him. Then, bafflement crossed Asgore's fuzzy features, as he caught sight of the three extras. Sans tensed up when the boss monster noticed him, while Flowey shrank back against Frisk, who smiled nervously.

“Who are you three?” he asked curiously.

“Is someone else there?” Alphys's counterpart asked over the phone.

What followed, my good reader, was the typical pattern of the situation; an introduction of the lookalikes, a basic explanation of crossovers, and bewilderment on the part of the person being explained at.

“I… golly, that's a lot to take in.” the towering boss monster said at last. “Are you all right? How are you all going to get back?”

Sans glanced at his blue-clad counterpart. “workin' on it.” he managed at last.

Asgore's face crumpled into an expression of deep sympathy. “Goodness! Do you need anything? Will you need a place to stay? By any chance, do you want some tea?” the part-time stuff of Sans's nightmares asked earnestly.

He turned to his ex, a pleading expression on his face. “I know it is a tad awkward, but if you do not mind, may I…?”

“I'm good.” the human in red piped up; Sans and Flowey both quickly nodded in agreement. “On the tea, that is. B-but thank you!”

Sans was in no hurry to accept an offer for a place to stay from Asgore Dreemurr, even a humble version of him that was hugged by small children and wanted to make tea for strangers. But the boss monster's idea made him wonder- what would they do, if they couldn't get back? Frisk and Flowey could easily persuade this world's Toriel to look after them for a little while, but Sans wasn't sure how much she'd trust him, or vice versa. Back in his home universe, everyone seemed to be tolerating each others' presences, which was a relief.

If it was just him and his counterpart worrying about how to sort things out, they'd probably do what they did last time, and sneak around, fiddling with a machine that made a habit of bending the laws of physics and hopefully not killing each other. With so many other people involved, however, that wasn't an option- not if they wanted to avoid more awkward questions whose answers had been erased from the timeline entirely.

The sound of his cellphone ringing derailed his train of thought. It startled most of the people in the room, as it was unusually loud. Then, Sans realized it wasn't a cellphone- _cellphones_ , more like, his and his counterpart's going off with such synchrony that they seemed to be producing the exact same sound, without any trace of an echo. He cast a hurried look at the other skeleton, who nodded almost imperceptibly.

Space was out to lunch again. And now that it was distracted, they could- hopefully- get everyone back to the right universe.

 

Meanwhile, in the other world, the spaghetti was coming along pretty well. Surprisingly, nothing had been destroyed yet, but that hadn't stopped the black-clad Undyne from trying to make a few bets with her counterpart over how damaged the kitchen would be when Toriel got back, and what the Queen of All Monsters would do to the two skeletons when she got back. The less edgy fish monster was up for wagering on the possible destruction, but the other point gave her pause. All of the “evil twins” she'd seen thus far had seemed just that- evil, at least formerly- and found her nefarious counterpart's predilection for punishment more than a little worrisome.

“What she'll _do_ to them?” she said, not sure at all what to expect from the Toriel of that world. “That's… kinda harsh, isn't it?”

The bigger robot rolled all four of his eyes, and shrugged theatrically with both pairs of arms. “ _Hardly_.” he said, smirking at the edgier fish monster with a fiendish gleam in his upper two eyes. “Undyne and Papyrus are the monsters who were surprised to learn… what was it? 'Friends don't kill friends', if I'm not mistaken?”

The less edgy fish monster's eye widened slightly, while the wilder, black-clad Undyne leapt up, slamming both hands down on the table as she glared at the taller Mettaton. “That- that wasn't a surprise! Frisk just wanted to make sure we all knew! You're exaggerating!” she shouted.

From the kitchen, the edgier skeleton called “STOP TRYING TO MAKE US LOOK BAD IN FRONT OF THE OTHER-WORLDERS, YOU TIN-PLATED LUNATICS!”

While the shorter, pinker Mettaton raised an eyebrow at yet another use of the plural directed at his counterpart, the less edgy Undyne wondered aloud, “Wait, is that why this Toriel's mad at your Sans? Did he try to kill a friend?”

At once, the conversation screeched to a halt, and what was left of it was smothered by a thick, baffled silence. Undyne shifted awkwardly in her seat; she saw that she'd clearly overestimated these monsters' knavery. Her counterpart and the taller robot exchanged a surprised look, while the sharp-toothed skeleton around to glare at her.

“WHO TOLD YOU ABOUT THAT?!” he demanded. His friendlier counterpart's sockets widened.

The edgier Undyne rolled her eyes. “Nah, Toriel's not mad at Sans over _that_.” she explained indifferently. “That's old news. Besides, we all tried to kill Frisk at some point, even her and Flowey!”

The taller robot's bottom set of eyes looked up, and the fingers on one of their lower hands tapped idly on the table, to the other Mettaton's clear confusion. “he did try to kill them after befriending them though…” they droned, in a very different voice. “no one else did that…”

The pinker Mettaton's eyes widened slightly in alarm. He gaped, and for a moment seemed to be about to speak, but couldn't find the right words.

“SHUT UP, NAPSTABLOOK!!!” the black-clad Papyrus roared. The taller robot rolled their lower set of eyes, before they suddenly dimmed and closed, and their lower pair of arms fell limp at their sides. Around them a gray haze appeared, which drifted away from the robot and materialized into the apathetic form of Napstablook.

“i'm not insulting him…” they said in their low voice. “i'm just saying… toriel might still be kinda mad at him over it…”

Before the edgy skeleton- who looked like he would outright explode if he got any madder- could bite the haunted robot's head off, or the pinker robot could try to get to the bottom of things, the less edgy fish monster changed the subject again.

“If that's not it, then why is she mad at Sans???” Undyne asked. She hoped her shock over hearing how casually everyone approached the subject of attempted murder didn't show; she'd be one to talk, she knew, considering how tenaciously she once tried to kill the Frisk she knew. Besides, if it wasn't attempted Friskicide, what was it that this Toriel could be that mad at Sans for? As far as Undyne could tell, the boss monster was the most reasonable- and normal- of the bunch.

Her counterpart snickered. “He smashed one of her pie dishes-”

“ACCIDENTALLY.” the angrier Papyrus interjected.

“SHUT UP, PAPYRUS, I'M DOING THE TALKING!” the black-clad fish monster shouted back. “And he forgot to tell her about it, or something, which pissed off Toriel even more, and now they're on bad terms again.”

She smirked at the sight of the other worlders' looks of bewilderment. “Papyrus took Sans's side like he always does,” she began. “Asgore tried to take Toriel's side like he always does to try to get back on her good side, which never works because we always ignore him when he tries to butt in like that, I sorta??? Took Sans's side??? 'Cuz we're friends, y'know, but Alphys thought Toriel had a better point-”

The taller, redder robot interrupted her. “As much as I loathe agreeing with Alphys,” he said pointedly, giving the mad scientist an exaggeratedly annoyed look where she still sat in the corner, ignoring all but her phone. “I saw things the same way.”

“i didn't…” they suddenly said in their monotonous voice. “i don't really care either way… they're always throwing tantrums over dumb stuff… even frisk keeps out and lets it blow over now…”

From the kitchen, the edgier skeleton let out an irritated exclamation while his counterpart strained the spaghetti. He stormed back into the main room to join the conversation properly.

“DUMB!” he declared. “TRY PUERILE! IMBECILIC! ASININE! THIS IS OUR STUPIDEST FEUD YET!”

As the black-clad skeleton ranted, the less edgy Undyne raised an eyebrow, sighed, and tried vainly not to be surprised, as her impression of not-Toriel being the least bizarre of the bunch shattered and crashed to the ground.

**Notes for the Chapter:**

> After his long string of successes in A Path to Redemption, at least one of Flowey's plans had to go nowhere.  
> Since I've always headcanoned that Gaster was Sans and Papyrus's father, I imagine Sans was helping him with his research and experiments for quite some time, up until the accident. Felsans, meanwhile, usually had to be roped into them when he would have preferred to be doing anything else.  
> In my outline, I think I originally had slated the explanation for the feud for Chapter 5. It kept getting pushed back when I couldn't fit it in. I'm kinda glad I kept it off this long, though.
> 
> Chapter 10, the really crazy one, will be up on Wednesday.
> 
> I just realized that back in Chapter 1 Sans was holding a bag of groceries and I never mentioned them again. They just came up while I was writing so I need to go back and make sure it's clear he's been hanging on to this stuff the whole fic.


	10. Chapter 10

**Summary for the Chapter:**

> Sans and Sans scramble to get everything back to normal, but they hit a few roadbumps along the way.

**Notes for the Chapter:**

> Time to play spot-the-Lord-of-the-Rings-shout-out!  
> When I first got the idea for this fic, I thought it'd be crazy, with lots of people crossing over all the time and all that jazz. It did have a lot of people getting shunted between universes, but this one feels a little more fast-paced (to me at least) and it's the kinda thing I had in mind when I conceptualized A Peculiar Crossroads. So it's a very important chapter to me.

“Sans? Why's your ringtone so loud?” Alphys asked the blue-clad skeleton curiously.

The edgier Sans pulled his own ringing phone out of his hoodie pocket. Frisk- the one in red and black- leaned over to see who was calling, hoping it would be someone they knew. Their eyebrows flew up in surprise.

“That- how is your phone even showing that number?” Flowey asked in amazement.

To the casual observer it looked like the black-clad skeleton's phone was malfunctioning terribly. The caller ID function in particular seemed to be going haywire. Meaningless strings of letters and numbers and other symbols flickered where the caller's name and number should have been displayed. Finally, the two calls ended just as simultaneously as they'd started.

The lizardy scientist looked from one Sans to the other. “Okay, question-” she began.

“possible answer.” the more chill skeleton deadpanned.

Alphys rolled her eyes and went on. “W-what happened? Did someone tr-try to call one of you again, and g-got both of you?”

“i mean… i guess.” the Sans she knew continued with a shrug. He mentally thanked Alphys for the convenient explanation. “if they did, i guess that means space is going nuts again.”

She stared at him, wide-eyed. “Uhh, sh-should we be concerned about that?” she asked faintly.

“nah.” the blue-clad skeleton said simply. “welp, time to go get papyrus and undyne.”

“an' we do this simultaneously?” his counterpart checked.

The Sans of that world nodded. “probably for the best.” he said.

“right. brat? daffodil?” the edgier skeleton said, with a sideways glance at his fellow other-worlders. No sooner had the words left his mouth than the human in red and black wrapped their arms around the edgier skeleton's arm. As pleasant and friendly as this world was, they were clearly ready to go back to their familiar, bickering one.

“'k.” the more chill skeleton said. “3… 2… 1…”

 

The world melted away to a nothing rocked by reverberations, and then into a room similar in layout but not in aesthetic. Two fish monsters, a pink robot, a mad scientist lizard, and a friendly-looking skeleton digging into a plate of spaghetti and meatballs were sitting around the table. The taller, redder Mettaton was standing close by, as none of the chairs were quite big enough for him. They all stared at the newcomers, wearing expressions that showed off the entire spectrum of surprise.

“FRISK! You WERE stuck over there!” the edgier Undyne shouted, while her counterpart raised an eyebrow at the sight of the human being so close to Flowey. “You okay, dude?!”

“SANS!! YOU'RE BACK!! ABOUT TIME!!” the friendlier Papyrus exclaimed happily.

The human, meanwhile, let go of the black-clad Sans's arm, and began looking around the room in confusion. “I'm fine. Where's Mom?” they asked.

“and where's MY brother?” the edgier Sans demanded. He ground his teeth in annoyance. “don't tell me…”

“Toriel not here; she's out looking for you, Frisk.” Alphys said, after she muttered a good-bye into her phone and put it away. The black-clad skeleton audibly sighed with relief at that news. “And, w-well, Sans… you all appeared right where your brother and Napstablook were standing. They disappeared right as you showed up. Is that normal?”

“ugh.” the edgier Sans groaned, holding his head in his hands. “again?! you've GOTTA be kidding me.”

The taller Mettaton drew himself up to his full height, upper pair of arms crossed, and looked down his nose at the skeleton. “You will bring them back, of course?” he said haughtily.

Sans glared indignantly back, sharp teeth clenched in an angry “what kind of moron do you take me for?!” sort of expression.

“howza 'bout we head outside next time we cross over?” his blue-clad counterpart suggested, as the monsters from the other world got up to join him (Papyrus hurriedly finished off his spaghetti before he did so). “it's less crowded. less likely to displace someone else that way.”

“whatever.” Sans growled through gritted teeth. “who's where, again? i don't wanna make any more trips than i have to.”

“well. i'm here.” his counterpart began unhelpfully. “so's papyrus and undyne. and mettaton.” He glanced at the monsters from that world. “who vanished when we showed up?”

“My cousin and Papyrus.” the red robot snapped.

“they're back in our world. think that's it. now're we ready?”

 

The sight of two Sans-es and the other Frisk and Flowey suddenly vanishing on its own was fairly startling for the monsters gathered at Toriel's house, and the instant arrival of a gray ghost and a tall skeleton in roguish raiment was even more shocking. No one even happened to notice that, visible through the unshuttered window, an unpleasant monster shaped vaguely like a UFO was plodding down the street.

“that was weird… what happened…?” the gray ghost asked, slowly looking around the room. They looked not so much surprised by as resigned to the situation.

The skeleton clenched his fists and loudly ground his teeth in aggravation. He looked meaner than the Papyrus that Toriel knew, even taking into account the fact that he was in high dudgeon at that moment. “SANS!!! I DON'T KNOW WHAT IT WAS, BUT IT HAD SOMETHING TO DO WITH SANS. GAH! I HATE IT WHEN THIS HAPPENS!!!”

On the table, the potted golden flower stared in amazement at the new arrivals. If only he lived in their world, he mused; a genuinely 'kill-or-be-killed' Underground must've been infinitely more entertaining than his own. A nice place to sit back and watch the world fall to pieces in horrible ways even without having to lift a vine to mess with it.

Toriel cleared her throat, hoping that the situation would soon be resolved and strangers would stop materializing in and around her house. “Excuse me.” she said authoritatively.

The skeleton turned around, and Toriel plainly saw that he was taken aback by the sight of Asgore Dreemurr. Not-Papyrus's skull tilted back, and his brow ridges furrowed as his sockets narrowed in wary suspicion. While he was facing Toriel, his gaze darted questioningly to the other boss monster. All of the monsters from the other world had reacted that way to her ex, and that was beginning to concern Toriel.

“I take it you two are from the…” Her eyes flitted to one side as she sought the right word. “other world?”

“YES.” not-Papyrus said tersely. “WE PROBABLY WON'T BE HERE LONG.” He scowled irritatedly. “IF SANS AND HIS COUNTERPART WOULD JUST GET THEIR ACT TOGETHER.”

“I see.” Toriel said simply, biting her lip.

An awkward moment passed, and then from outside the assembled monsters heard a muffled conversation coming from outside.

“FINALLY!!!” Papyrus- the more cheerful one- exclaimed. “SANS, WE ARE NEVER DOING THIS AGAIN.”

“it wasn't that bad, bro. we're lucky we _cut it short_ when we did.” Sans said, suppressing a laugh.

“SANS!! I'M BEING SERIOUS!” Papyrus complained, while Sans's counterpart snickered. “WE'RE EVEN LATER THAN WE WOULD'VE BEEN IF WE'D JUST DRIVEN! I HOPE YOU'VE LEARNED SOMETHING FROM THIS, LAZYBONES!”

“pfft.” Sans's rolling of his eyes was practically audible. “what?”

“SHORT CUTS MAKE FOR LONG DELAYS! NYEH HEH HEH!” Papyrus announced, quoting something he'd heard elsewhere. Within Toriel's house, his counterpart scoffed, and one corner of his mouth turned up in disgust.

“UNBELIEVABLE.” he muttered.

 

The edgier versions of Sans, Papyrus, and Napstablook got ready to return to their own world, and all versions of everyone involved was already more than ready for things to return to normal, and of course they were all blissfully unaware of what had been out on the street when the two Sans-es and company had last crossed over.

A thoroughly aggravating monster, who looked a bit like a gourd that'd been left out to sit for too long, had by chance been strolling along- if, my good reader, one can use so pleasant a word for such a monster- to the exact spot on Toriel's house that our protagonist herd appeared at. Of course, when they appeared, space gave them a stern look and decided that they couldn't just be in the same place as Jerry, and pushed the offending monster out of the way.

Jerry was not often subjected to situations as unpleasant as he was, and he was even less used to seeing doppelgängers of himself. While heavier footsteps were coming up behind him, in front of him another squat and shifty-eyed person, monstrous in multiple senses of the word and hideous in clashing shades of red and black paint, was trudging toward him.

This Jerry stopped short. The two monsters stared at each other, dumbstruck.

“Ugh.” the red-and-black Jerry said with a sneer, before turning tail and trudging back the way he'd come.

“Laaaame.” the slightly less wretched Jerry groaned. He only backed up a few steps, not doing much to ditch his counterpart although that was exactly what he wanted to do; but he was still pretty discombobulated, and besides, it's the thought that counts.

A moment later, the heavier footsteps abruptly stopped mid-step, and two skeletons and a ghost manifested out of nowhere behind the obnoxious monster.

“SANS.” the tall skeleton said.

“y-yeah?” the shorter one said in an uncertain voice.

“WHAT. IS. THAT?!”

“it's jerry… two of him…” Napstablook said, voice tinged with disgust. “send one back…”

The short skeleton snarled with frustration. “not on your life, moron. i'm not going anywhere near that freak of nature.”

Napstablook slowly dragged their gaze from Jerry to Sans. “if you don't… we'll have to deal with two of him… send one back…”

“c'mon, ya goons, gimme a break.” Sans growled, glaring daggers at his brother and the ghost.

“SANS, OH MY GOSH, JUST SEND HIM BACK ALREADY, ORRRR- HRMPH.” Papyrus said, shaking his head slightly to cut off the threat born of unfortunate habit. “JUST DO IT, SANS!!!”

Jerry, having heard their conversation, had turned around and was staring at Sans with beady eyes. He looked very unimpressed. Sans's sockets went dark.

**Notes for the Chapter:**

> Writing skeleton expressions is hard.  
> Papyrus hates puns when he's not the one making them. As a side-note, I figure that if UT!Papyrus tends to express his distaste for something but then change his tune if a friend turns out to like it, then Felpyrus tends to express his liking for something and change his mind if someone else agrees, just to annoy them.
> 
> And so the grand tradition of ditching Jerry continues. This time, he even ditches himself!
> 
> Universal headcount: Jerry from Undertale is in Underfell, but as far as the characters know everyone else is back in the right universe at last. Are they correct in assuming so? Stay tuned for the finale in Chapter 11, this Sunday.


	11. Chapter 11

**Summary for the Chapter:**

> The hectic crossovers wind down, but there's still a few more mysteries to clear up before everything can come to an end.

**Notes for the Chapter:**

> Parting is such sweet sorrow.

While she had certainly witnessed some strange things that day, the darkly dressed Queen of All Monsters had not for one second expected to be directly involved in them. But as she walked back to her house, without having seen any sign of Frisk or Flowey, something supremely disagreeable happened. Besides seeing that Jerry was approaching, that is.

Without any warning, Toriel was thrust into a world of nothingness wracked by powerful tremors, as if somehow an earthquake was taking place in the fabric of time and space. Then, with a feeling that she could best describe as what being turned inside out must be like, she was suddenly back on solid ground on a vaguely familiar street.

Toriel heaved a sigh, wearing an expression of dignified exasperation. What to do now?, she wondered. The house that looked so much like her own undoubtably belonged to her own double, and she could not help but feel curious as to what the other version of herself was like. Something must have gone differently in this universe to make everyone so different; had she still left Dreemurr? Had he been less cruel? Had Asriel and Chara not- were her first two children alive, here?

She knew such speculation was useless, dredging up painful memories and false hopes and doing nothing to help her get back to her own world, but they were enough to keep her fixed where she was for a few moments. The door of the house opened, and as she'd expected Toriel found herself face to face with herself. And lingering behind, looking curiously over her double's shoulder, was the twin of her former husband.

Toriel's double may have lived in a more peaceful world, but Toriel could tell they had shared many of the same sorrows. If she was still with her Asgore, they would have greeted Toriel together, not apart like this. Whatever event it was that had distinguished their worlds, it had obviously occurred alongside her leaving Dreemurr.

“Greetings.” the other matriarch said, a bemused smile on her face. Another Frisk shuffled over to stand beside her, but there was no sign of a Flowey, which seemed odd; Toriel's children were nigh inseparable.

“Greetings.” Toriel said in return. “Are my children here?” she asked.

Her double's eyebrows raised every so slightly in brief surprise, before she shook her head. “They _were_ here, but a few moments ago. The Sans of your world took them back to your home.”

“That is good.” Toriel said. This was one of the strangest conversations she had ever had, she reflected inwardly, in a long life full of strange things. “And if they have just gone back, then hopefully I shall return home as well.”

The bizarre conversation came to an abrupt end when- speak of the devil- Sans was suddenly there right next to her. Toriel did not see him arrive, nor did she hear anything- a faint scratching sound, perhaps, but so quiet it could have been anything- he was simply there, tense and seething. Jerry, of all monsters, was with him.

“if i never live to see another crossover it'll be too soon!!!” the incensed skeleton snarled, voice dripping with loathing, as Jerry walked away. Surprise flashed across his face when he realized who else was there.

“wh- toriel?” he said.

“Sans.” she acknowledged with a small nod. “You know how to get home, do you not?”

The short skeleton nodded. “yeah. hopefully it'll work the first time.” He clenched his sharpened teeth. “if it doesn't i'm just gonna keep trying til it does. let's get outta here.”

Toriel wanted to ask Sans what that would entail, but before she could say anything the world faded out to nothing, and then nothing faded in to their own street.

 

“WHO WAS THAT?” Papyrus asked, once Toriel had gone back inside.

Toriel exhaled sharply, blinking in bewilderment. “Myself, that time. And the other Sans. Again.” she said at last. “I think everyone is in the proper place, now.”

Everyone present- Sans, Papyrus, Toriel, Frisk, Undyne, Alphys, Napstablook, Mettaton, and Asgore- well, everyone save Flowey- breathed a sigh of relief. It had not been so bad, meeting their counterparts, but they were all very ready for their weekend to go back to being more or less predictable. A relaxed silence fell.

“Well, darlings, it was nice seeing you all, I'm afraid I have to go. Shows to coordinate, music to mix.” Mettaton said at last, heading to the door with Napstablook trailing behind him. “My next productions won't write themselves! Toodles!”

Alphys got up from the table and walked to Undyne's side. “I, uh, guess we'd b-better get out of the way, t-too.” she said hurriedly, taking her girlfriend's hand and heading to the door. “B-besides, I've got a lot of questions for my c-counterpart- I want to talk to her b-before space goes back to being completely normal!”

“if you're just calling yourself i don't think that's a-” Sans began; the door heavily swung shut in the lizard monster's haste to go figure things out. “-and she's gone.”

“Boy! This sure has been a strange day.” Asgore said, still looking somewhat baffled. “It was very nice seeing you all. But now, I suppose it's my turn.”

Frisk went up and gave him another hug, and the former king nodded to each of the others before heading out.

Papyrus glanced at a clock to see what time it was, and his sockets flew wide open in amazement. “WOWEE! IT'S BARELY PAST NOON!” he exclaimed. “THERE'S STILL PLENTY OF TIME FOR BAKING!!”

“yeesh. feels later than that.” Sans said lazily. He winked. “you guys have fun. i'm just gonna take a nap. might join ya later, but keep it down, would ya? kinda wanna just _rest in peace_ for a while.”

Toriel raised an eyebrow.“You do look _dead_ tired.” she began, as a grin irrepressibly grew across her face. “We'll try to avoid doing anything that would give rise to a rude a- _bakening_.”

Papyrus exhaled sharply in annoyance at their shenanigans. He scooped the bag of groceries off the table and strode away to the kitchen, while Sans plodded over to the still-open front door. Knowing him, he probably to end up crashing on the sofa in the other room.

“SUIT YOURSELF, LAZYBONES!” he shouted, and Frisk rushed off to join him.

Sans did indeed drop himself off on the sofa, but he did not drop off to sleep- at least not right away. First, he pulled out the strange note from earlier, unfolded it, and began to read the peculiar scrawl. The note was a long one; it started off with an apology for the stress and for the inconvenience, but most of it was an explanation of the morning's bizarre events.

The first crossover had been a mistake. Alone for so long in the void, the two instigators had become aware of each other by chance; when they tried to interact, they'd inadvertently entangled their universes, causing shortcuts to leave one universe and lead to the lower space of the other. They'd scrambled to fix their mistake- although, according to the note's author, his counterpart was more reckless, more twisted by his ordeal, and more willing to let things drag out for his own amusement.

This one, on the other hand, had been entirely intentional- with the purpose of sending the messages Sans and his counterpart had discovered. They'd had to destabilize space more often this time around, to give themselves enough time to write their notes in full- even interfering with shortcuts to achieve that end, to force Sans and Sans to keep crossing over. After that they'd had to back off from meddling for a bit. When Sans had called Papyrus across universes, the instability had broken up their call by scrambling the signal's destination, sending it every which way across both universes. Not exactly an ideal setting for teleportation (well, the note's author had thought so- his counterpart, apparently, had been perfectly willing to keep going).

The explanation came to a hurried close. A little farther down the page was another message, in a clearer, larger script- the message that had caused it all, Sans figured. As he started reading it, his sockets widened, and his breath hitched. He stared at it for a moment, then re-read it. He wanted to remember this, if someday things came undone again. It was succinct- but it was enough.

“I miss you two,” the last section of the note read. “I miss you and I'm very proud of you. Please, try to enjoy what you've got. Please believe me when I say that it's going to last this time around.”

 

Somehow, Sans felt exhausted as he and Toriel walked back to her house, even though all he'd done that morning was move around without actually moving, which was usually the least tiring thing he could do. He was lagging behind, not sure if he was welcome, although he did at least want to sneak in to get Papyrus and figure out what to do next.

“So, I hear that you helped get everyone back here, in the end?” Toriel inquired unexpectedly as she reached the door, breaking into the silence that had fallen.

Sans, taken aback, stopped short blinked in surprise. He fidgeted a bit where he stood. “yeah…?” he said tiredly, wondering what she was getting at.

“Well. Thank you, for looking after Frisk and Flowey.” the Queen of All Monsters said, turning to face him. She inhaled slowly. “Would you like to come in?”

“uh, sure.” the short skeleton said. He assumed that the boss monster had finally decided to give up and forgive him for their latest feud (at the rate they came up with and then uneasily settled arguments, they were going to have to switch their hatchet burial ground over to standing room only). Sans was going to take advantage of the ceasefire while it lasted.

Inside, no one showed any signs of maybe meaning to leave soon (although if Toriel still had work to do that day, particularly if it concerned her orphanage, she'd probably herd them out eventually). They were too busy watching Toriel- she'd hardly had a chance to enter the house, before her expression ran the gamut from blank surprise, to irritation, to regal disapproval as she noticed Papyrus, realized what he was up to, and prepared to confront him.

“Papyrus, what on Earth are you doing to my kitchen!? Whatever happened to 'best behavior?” she loudly demanded from near the doorway, one hand on the still-open door.

“I'M CLEANING UP.” the tall skeleton said brusquely. Sans, meanwhile, slunk inside. “I'M ALMOST DONE.”

Toriel's eyes narrowed, and her mouth a thin hard line. After everything that had happened that day- and now coming home to _this_ \- she was sorely tempted to slam the door shut with all of her might. But, no; that was immature at the best of times, and besides, Sans was nearby. Although he was good at covering things up, she knew he was easily alarmed.

“That pot had better be spotless!” she said instead, hurrying over to see if any damage had been done.

“OF COURSE IT IS!!! WHAT KIND OF JERK DO YOU TAKE ME FOR?” Sans heard his brother answer, as he snuck away to another room unnoticed.

He sat heavily down in an armchair. The skeleton left the lights off; he didn't want to attract attention. Sans sighed tiredly, and fished the badly-creased paper back out of his pocket. Part of him wanted to just toss it in the paper shredder and be done with it, but… “This won't fix anything?” His curiosity got the best of him, and he carelessly unfolded it just enough to read it in the light spilling in from the main room. There wasn't much to look at; just a paltry few lines in a distinctive scribble at the top.

As he read, he felt his innards clench (well, he would've, if he had any, but in spite of this lack the feeling was more or less the same) and he raised a brow ridge suspiciously. What had brought _this_ change on? It was not what he'd expected.

“There's not much I can say for myself.” the note began. “This won't fix anything. I understand that much. And I also understand if you can't accept this. But, I'm sorry. For absolutely everything.”

Sans clenched his jaw and stared at the message for a moment, then re-read it. Sans figured some part of him appreciated it, but the note's author was right about one thing; Sans wasn't about to forgive him, at least, not anytime soon. With more time, maybe he'd move past it, but not yet.

Another line of writing suddenly caught his notice; much farther down the page from the rest. It had been haphazardly written near the bottom (although Sans couldn't fathom how).

“PS you were right Alphys DID do it, don't know why” it said. The skeleton rolled his sockets. Was he being serious? Sans honestly couldn't tell. The writer's generally demeaning demeanor toward everyone around him probably had something to do with it. And his habit of terrorizing people (although, that one had been pretty typical for monsters back then). And Alphys's own ambition. And… everything.

Welp. He'd go back to dealing with that later. Sans shoved the message back in his pocket and headed back to the main room; it was as nice a spot for a nap as any. Besides, no one else showed any signs of leaving, so why should he? No one was angry at anyone at the moment and he was going to take advantage of it as much as possible while it lasted.

A stray worry flitted onto his train of thought; what if it didn't last? More to the point, what if things suddenly went back to looping again?

Sans shoved it away. He could go back to dealing with _that_ later, too. Until proven otherwise, he was going to just assume tomorrow was another day, that wasn't going anywhere.

**Notes for the Chapter:**

> I can't believe the final chapter is finally here. I don't think I ever thought my story would ever get this long, let alone get this much attention (you people are all absolutely wonderful!!!). I'm kinda sad to see it go, but it's been what, five whole months? I think today is almost exactly five months since I started writing the whole series. HUGE thank-yous to everyone who's been reading this (seriously, kudos and comments are what fuel these things). I'm amazed and gratified that so many people liked this series.
> 
> Sorry for the posting delay- this day got unexpectedly busy somehow. :(
> 
> Yes, Torifel runs an orphanage rather than a school (tho I imagine she'd see to the kids' education nonetheless). Underfell probably left a lot of orphans behind, and since monsters and humans aren't mingling as quickly as in Undertale I felt that it made more sense. I wish I'd been able to bring it up sooner.
> 
> The idea that the Gasters were using the crossovers to get a message out to Sans came to me when I realized that pretty much every single Underfell character had gotten a redemption arc, or at least seen the error of their ways and come to terms with that even if they aren't really "good" yet (as with Felgore)- except for Underfell Gaster. He was still a terrifying bogeyman cackling maniacally in the void, and that didn't sit right with me (if Felgore, the one behind pretty much everything nasty in Underfell, could get an okay ending, then why not Gaster?), and so the apology-note subplot was born. If he ever makes a return, it will take many years for him to even begin to actually patch things up with everyone, but at least he'd be willing to try to atone.
> 
> I hope that the way I wrote UT!Gaster's message to Sans sits right with everyone. I left some of the crossover details vague because doing otherwise would involve making up technobabble, and might break suspension of disbelief and remove some of the mystery/magic of it all.
> 
> Now that the whole series is finished I'll finally have time to go back and polish the last two up some more (the way I did for A Novel Experience); mostly just making sure everything flows as well as possible/general proofreading, but also maybe adding a few things that I wanted to include the first time around but couldn't find room for (nothing too big though).
> 
> If anyone has any questions about other Underfell details (since I didn't touch too much on some of the backstory) please ask away in the comments, I'll be happy to answer.
> 
> Again, thank you to everyone who read this!!! It's been an amazing ride!


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